OFFSET
1,2
COMMENTS
The asymptotic density of this sequence is Product_{p prime} f(1/p) = 0.87686263163054480657..., where f(x) = 1 - x + (1 - (1-x) * Product_{k>=0} (1-x^(2^k)))/2. - Amiram Eldar, Oct 27 2023
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..10000
Vladimir Shevelev, S-exponential numbers, Acta Arithmetica, Vol. 175 (2016), 385-395.
MATHEMATICA
odiousQ[n_] := OddQ[DigitCount[n, 2, 1]]; Select[Range[100], AllTrue[FactorInteger[#][[;; , 2]], odiousQ] &] (* Amiram Eldar, May 18 2023 *)
PROG
(PARI)
A355825(n) = factorback(apply(e->(hammingweight(e)%2), factor(n)[, 2]));
isA270428(n) = A355825(n); \\ Antti Karttunen, Jul 21 2022
(Scheme, two variants, both requiring Antti Karttunen's IntSeq-library)
(define A270428 (NONZERO-POS 1 1 chA270428))
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Antti Karttunen, May 26 2016
STATUS
approved