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 A275491 Number of primitive weird numbers (A002975) below 10^n. 4
 0, 0, 1, 2, 7, 13, 24, 48, 85, 152, 277, 499, 881 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,4 COMMENTS It is not known unconditionally whether there are infinitely many primitive weird numbers (PWN; A002975), although numerical data provides strong evidence: even the number of weird numbers of the form 2^k*p*q (A258882, A258333) seems to increase rapidly as k increases. G. Melfi has shown that Cramer's conjecture implies the infiniteness of PWN. Partial sums of A275492. LINKS Table of n, a(n) for n=0..12. G. Melfi, On the conditional infiniteness of primitive weird numbers, Journal of Number Theory, Volume 147, February 2015, Pages 508-514. PROG (PARI) s=0; vector(22, n, s+=sum(n=10^n\20+1, 10^n\2, is_A002975(n*2))) (PARI) vector(22, n, #select(t->t<10^n, A002975)) \\ If A002975 is defined as set, vector, or list with enough terms. CROSSREFS Cf. A002975, A006037, A258333, A275492, A275493, A275494. Sequence in context: A045377 A180470 A182415 * A360673 A183435 A360385 Adjacent sequences: A275488 A275489 A275490 * A275492 A275493 A275494 KEYWORD nonn,more AUTHOR M. F. Hasler, Jul 30 2016 EXTENSIONS a(12) from Robert G. Wilson v, May 25 2018 STATUS approved

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Last modified June 4 21:13 EDT 2023. Contains 363130 sequences. (Running on oeis4.)