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%I #9 Feb 13 2022 13:38:32
%S 13,37,61,73,97,109,153,157,181,193,229,241,277,313,325,337,349,373,
%T 397,409,421,433,457,541,577,601,613,661,673,709,733,757,769,801,829,
%U 853,877,925,937,997,1009,1021,1033,1069,1093,1117,1129,1153,1201,1213,1237,1249,1297,1321,1381,1429,1453,1489,1525,1549
%N Odd numbers for which sigma(k) is congruent to 2 modulo 4 and the 3-adic valuations of k and sigma(k) are equal.
%H <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a>
%t Select[Range[1, 1500, 2], Mod[(s = DivisorSigma[1, #]), 4] == 2 && Equal @@ IntegerExponent[{#, s}, 3] &] (* _Amiram Eldar_, Feb 13 2022 *)
%o (PARI) isA351536(n) = if(!(n%2),0,my(s=sigma(n)); (2 == (s%4)) && (valuation(n,3) == valuation(s,3)));
%Y Intersection of A191218 and A349749. Cf. A349755 (subsequence).
%Y Cf. A000203, A007949, A351534.
%K nonn
%O 1,1
%A _Antti Karttunen_, Feb 13 2022
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