A055708 Numbers n such that n - 1 | sigma(n).

2, 3, 10, 136, 32896, 2147516416

Offset: 1

Author

Robert G. Wilson v, Dec 04 2000

Keywords

• nonn
• more

Comments

a(7) > 10^13. - Giovanni Resta, Jul 13 2015

Crossrefs

Cf. A000203, A045768, A056006.

Programs

Mathematica

Do[ If[ Mod[ DivisorSigma[1, n], n - 1] == 0, Print[n] ], {n, 2, 10^8} ]

PARI

is(n)=sigma(n)%(n-1)==0 \\ Anders Hellström, Aug 15 2015

Extensions

a(6) from Donovan Johnson, Nov 15 2009