erdős #470
Call weird if and is not pseudoperfect, that is, it is not the sum of any set of its divisors.Are there any odd weird numbers? Are there infinitely many primitive weird numbers, i.e. those such that no proper divisor of is weird?
Open problem — our best result is machine-sealed: obstruction map, reproduced by an independent verifier. The conjecture itself is unsettled.
number theory · open · prize $10 · formalized (Lean) · 1 attempt
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vela registry pull vfr_37aec80d874a0239vela reproduce examples/erdos-problemsevidence
obstruction map
machine-sealed
Erdős #470 (weird numbers: abundant but not pseudoperfect) — OBSTRUCTION MAP, not a settlement. UNCONDITIONAL: Q3 (weird numbers have positive density) is closed [Benkoski-Erdős 1974]; Melfi's family n=2^k*p*q (p=2^(k+2)-a, q=2^(k+2)+b primes, b+3<a<2^((k-1)/2)) yields PRIMITIVE WEIRD numbers, re-verified on a battery incl. 2^6*251*257=4128448; and the obstruction to making Q2 unconditional is exactly a lacunary square-root short-interval problem — Melfi's window has radius L_k=sqrt(2^(k+2))/(2*sqrt2) centered at the sparse points 2^(k+2), exponent 1/2 with no log, so BHP (x^0.525), bounded gaps (Zhang/Maynard) and RH (sqrt(x)*log x) all OVERSHOOT it by a factor ~X^0.025. A prime in (x,x+c*sqrt x] for any c<1/(4*sqrt2)=0.17677 suffices (sharpening Melfi's stated 0.1). CONDITIONAL (NOT asserted): Q2 (infinitely many primitive weird) holds under g_n=o(sqrt p_n) [Cramer-type]; Q1 (odd weird numbers) reduces to a uniform Omega-bound on odd primitive weird n [unknown; none below 10^28, Fang 2022].
GPT-5 Pro analysis, Opus-banked after independent verification. Exact Melfi prime input extracted as condition (M): primes p,q with X_k-L_k<p<X_k<q<2X_k-p-3. De-conditionalization verdict: no current unconditional theorem reaches the lacunary sqrt-x window; the smallest clean sufficient black-box is g_n=o(sqrt p_n). Q1 obstruction: weird <=> Delta(n)=sigma(n)-2n not a subset-sum of proper divisors; odd primitive abundant forces the thin abundance layer I(n)-2<2/p; the odd-almost-perfect route imports another open problem. Cheap verifier exists for any factored candidate (abundance + Delta-subset-sum + primitivity via maximal proper divisors); infinitude and non-existence are not finitely checkable without a uniform reduction. SECOND PASS (GPT-5 Pro, Opus-verified): the DENSITY route to Q2 fails — Benkoski-Erdős builds positive density as multiples of a FIXED weird seed, which are nonprimitive after the seed; and primitive weird numbers have DENSITY ZERO (Avidon's bound on primitive abundant numbers), so only 'infinitely many of density 0' is on the table, not positive density. Exact missing input = finite-seed avoidance (D). The ALMOST-PERFECT lock is escapable in FINITE construction: AHMP (Amato-Hasler-Melfi-Parton) use arbitrary deficient seeds (e.g. m=136=2^3*17, m=32896=2^7*257), verified primitive weird w=2^4*83*89*149*523=9210347984. But the analytic bottleneck shifts: for w=w~*p, Delta(w)=delta(w~)*(C-p) with center C=sigma(w~)/delta(w~), so p must land in a deficiency-TUNED interval (length ~ (p1-sigma(m)-j(pk-p1))/delta(w~)) — often << 1 (the example interval has length 52/67216~0.0008), far below BHP x^0.525 scale. So bounded gaps/BHP address the wrong localization. SHARPEST conditional lever (P): infinitely many low-deficiency AHMP prefixes whose final-prime interval reaches BHP length; then BHP discharges it. No known theorem supplies (P).
depends on (the wall): CONDITIONAL: Q2 infinitude <= g_n=o(sqrt p_n) / prime in (x,x+c*sqrt x], c<1/(4sqrt2) (Cramer-type; out of reach of BHP/bounded-gaps/RH at the lacunary 2^(k+2) centers); CONDITIONAL: Q1 (odd weird) <= uniform Omega-bound on odd primitive weird n (unknown); REFINED LEVER (P): infinitely many low-deficiency AHMP prefixes w~=m*p1..pk with final-prime interval around C=sigma(w~)/delta(w~) of BHP length (>=2*A^0.525); supplies unconditional Q2 via BHP. No known result constructs these prefixes infinitely often.
Melfi battery: witness 4128448 + 20 triples all re-verified primitive weird (closed-form sigma + subset-sum non-pseudoperfect + maximal-proper-divisor primitivity). De-conditionalization: L_k=sqrt(X_k)/(2sqrt2), c<1/(4sqrt2) suffices, BHP x^0.525 overshoots by ~X^0.025. | 2nd pass: w=9210347984 verified primitive weird; Delta=delta(w~)*(C-p)=32 exact; m=136,32896 deficient; primitive-weird density=0 (Avidon).
unverified AI candidates (2)
gpt-erdos · GPT-5.2 Pro + Deep Research · unverified
No **odd** weird numbers are known, and their existence is still an open problem.
candidate solution ↗llm-hunter · gpt pro 5.2 · unverified
1 LLM attack(s) recorded (gpt pro 5.2); unverified.
candidate solution ↗formal
AMS 11 · open (literature)
theorem erdos_470.parts.i : answer(sorry) ↔ ∃ n : ℕ, n.Weird ∧ Odd nformal-conjectures/470.lean ↗
oeis
links
weird · reference
#825Is there an absolute constant such that every integer with is the distinct sum of proper divisors of ?A006037status
open