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%I #9 Feb 13 2022 13:38:38
%S 5,13,17,29,37,41,53,61,73,89,97,101,109,113,137,149,157,173,181,193,
%T 197,229,233,241,245,257,269,277,281,293,313,317,325,337,349,353,373,
%U 389,397,401,409,421,425,433,449,457,461,509,521,541,557,569,577,593,601,605,613,617,637,641,653,661,673,677,701,709
%N Odd numbers k that are not multiples of 3 and for which sigma(k) is congruent to 2 modulo 4.
%C a(25) = 245 = 5* 7^2 is the first term that is not prime.
%H <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a>
%t Select[Range[1, 700, 2], !Divisible[#, 3] && Mod[DivisorSigma[1, #], 4] == 2 &] (* _Amiram Eldar_, Feb 13 2022 *)
%o (PARI) isA351535(n) = ((n%2) && (0!=(n%3)) && (2 == (sigma(n)%4)));
%Y Intersection of A001651 and A191218. Complement of A351533 in A191218.
%Y Cf. A002144 (subsequence).
%K nonn
%O 1,1
%A _Antti Karttunen_, Feb 13 2022
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