OFFSET
1,2
COMMENTS
Odd numbers whose prime factorization has an even number of prime powers p^e with p == 1 (mod 4) and e odd. - Amiram Eldar, Apr 05 2024
LINKS
MATHEMATICA
Select[2*Range[120] - 1, Divisible[DivisorSigma[1, #^2] - 1, 4] &] (* Amiram Eldar, May 16 2022 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen, May 16 2022
STATUS
approved