A263983 Odd integers k such that sigma(k)^2 is divisible by k.

1, 1521, 5733, 92781, 108927, 544635, 628849, 1886547, 2069613, 2723175, 2876211, 5659641, 16978923, 40847625, 45623655, 50936769, 60998353, 84418425, 84894615, 89162541, 173369889, 182995059, 191166885, 262840851, 401164731, 424473075, 426988471

Offset

1,2

Comments

Odd terms of A263928.

Links

Table of n, a(n) for n=1..27.

Mathematica

fQ[n_]:=IntegerQ[DivisorSigma[1, n]^2/n]; Select[Range[1, 1886547, 2], fQ[#]&] (* Ivan N. Ianakiev, Nov 03 2015 *)

Prog

(PARI) lista(nn) = forstep(n=1, nn, 2, if (denominator(sigma(n)^2/n) == 1, print1(n, ", ")));

Crossrefs

Cf. A000203, A017665, A017666, A263928.

Sequence in context: A025413 A025410 A103962 * A031756 A226702 A318791

Adjacent sequences: A263980 A263981 A263982 * A263984 A263985 A263986

Keyword

nonn

Author

Michel Marcus, Oct 31 2015

Extensions

a(21)-a(27) from Ivan N. Ianakiev, Oct 31 2015

Status

approved