A239993 Numbers n such that n*sigma(n) is not divisible by 6.

1, 4, 7, 9, 13, 16, 19, 25, 28, 31, 37, 43, 49, 52, 61, 64, 67, 73, 76, 79, 81, 91, 97, 100, 103, 109, 112, 121, 124, 127, 133, 139, 148, 151, 157, 163, 169, 172, 175, 181, 193, 199, 208, 211, 217, 223, 225, 229, 241, 244, 247, 256, 259, 268, 271, 277, 283, 289

Offset

1,2

Comments

A000594(a(n)) cannot be 0 because 24 divides A000594(n) - n^4*sigma(n) for any n.

Links

Table of n, a(n) for n=1..58.

Mathematica

Select[Range[289], ! Divisible[#*DivisorSigma[1, #], 6] &]

Prog

(Magma) [n: n in [1..289] | not IsZero(n*SumOfDivisors(n) mod 6)];
(PARI) for(n=1, 289, if(!Mod(n*sigma(n), 6)==0, print1(n, ", ")));

Crossrefs

Supersequence of A002476. Cf. A000594.

Sequence in context: A243175 A352272 A229848 * A332335 A310961 A385829

Adjacent sequences: A239990 A239991 A239992 * A239994 A239995 A239996

Keyword

nonn

Author

Arkadiusz Wesolowski, Mar 30 2014

Status

approved