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A275492 Number of primitive weird numbers (A002975) between 10^n and 10^(n+1). 3
0, 0, 1, 1, 5, 6, 11, 24, 37, 67, 124, 223 (list; graph; refs; listen; history; text; internal format)



It is not known unconditionally whether there is an infinite number of 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 fast as k increases. Melfi has shown that Cramer's conjecture implies infiniteness of PWN.


Table of n, a(n) for n=0..11.

G. Melfi, On the conditional infiniteness of primitive weird numbers, Journal of Number Theory, Volume 147, February 2015, Pages 508-514.


(PARI) a(n)=sum(n=10^n\2+1, 5*10^n, is_A002975(n*2)))


Cf. A002975, A006037, A258333, A275491, A275493, A275494.

Sequence in context: A236387 A039918 A020685 * A046828 A328095 A046830

Adjacent sequences:  A275489 A275490 A275491 * A275493 A275494 A275495




M. F. Hasler, Jul 30 2016



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Last modified December 10 04:15 EST 2019. Contains 329885 sequences. (Running on oeis4.)