A351534 Odd numbers for which sigma(k) is congruent to 2 modulo 4 and the 3-adic valuation of k is one larger than the 3-adic valuation of sigma(k).

45, 261, 369, 909, 1017, 1233, 1341, 1557, 2313, 2529, 2637, 2853, 3177, 3501, 3609, 4149, 4293, 4581, 5121, 5445, 5553, 5733, 5769, 5877, 6093, 6525, 6849, 7173, 7389, 7713, 8361, 8469, 8793, 9117, 9225, 9441, 9981, 10629, 10737, 10953, 11061, 11601, 11709, 12249, 12357, 12681, 12897, 13005, 13329, 13977, 14517

Offset: 1

Author

Antti Karttunen, Feb 13 2022

Keywords

• nonn

Links

• Index entries for sequences related to sigma(n)

Crossrefs

Subsequence of A351533, which is intersection of A008585 and A191218.

Cf. A000203, A007949, A351536.

Programs

Mathematica

Select[Range[1, 15000, 2], Mod[(s = DivisorSigma[1, #]), 4] == 2 && IntegerExponent[#, 3] - IntegerExponent[s, 3] == 1 &] (* Amiram Eldar, Feb 13 2022 *)

PARI

isA351534(n) = if(!(n%2),0,my(s=sigma(n)); (2 == (s%4)) && (valuation(n,3) == (1+valuation(s,3))));