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A351536
Odd numbers for which sigma(k) is congruent to 2 modulo 4 and the 3-adic valuations of k and sigma(k) are equal.
2
13, 37, 61, 73, 97, 109, 153, 157, 181, 193, 229, 241, 277, 313, 325, 337, 349, 373, 397, 409, 421, 433, 457, 541, 577, 601, 613, 661, 673, 709, 733, 757, 769, 801, 829, 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
OFFSET
1,1
MATHEMATICA
Select[Range[1, 1500, 2], Mod[(s = DivisorSigma[1, #]), 4] == 2 && Equal @@ IntegerExponent[{#, s}, 3] &] (* Amiram Eldar, Feb 13 2022 *)
PROG
(PARI) isA351536(n) = if(!(n%2), 0, my(s=sigma(n)); (2 == (s%4)) && (valuation(n, 3) == valuation(s, 3)));
CROSSREFS
Intersection of A191218 and A349749. Cf. A349755 (subsequence).
Sequence in context: A140112 A089030 A351537 * A354467 A141122 A068228
KEYWORD
nonn
AUTHOR
Antti Karttunen, Feb 13 2022
STATUS
approved