A056076 Numbers k that divide sigma(k) + d(k), where d(k) is the number of divisors of k and sigma(k) is their sum.

1, 3, 14, 52, 60, 130, 184, 656, 5472, 8648, 12008, 34688, 2118656, 2500704, 33721216, 40575616, 59376256, 89397016, 99523456, 134438912, 150441856, 173706136, 283417216, 537346048, 1082640256, 6801628304, 91707741184

Offset

1,2

Comments

a(28) > 2*10^11. 14451706793984, 2258918614925312 and 9007202811510784 are also terms. - Donovan Johnson, Feb 10 2012

a(28) > 10^13. - Giovanni Resta, Nov 13 2019

Links

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

Mathematica

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

Prog

(PARI) for(n=1, 10^8, if(Mod((sigma(n)+numdiv(n)), n)==0, print(n)))

Crossrefs

Cf. A000203, A000005.

Sequence in context: A322199 A192882 A351690 * A117133 A238226 A083874

Adjacent sequences: A056073 A056074 A056075 * A056077 A056078 A056079

Keyword

nonn

Author

Robert G. Wilson v, Jul 26 2000

Extensions

Corrected by Jason Earls, Aug 06 2001

Corrected by T. D. Noe, Nov 01 2006

a(25)-a(27) from Donovan Johnson, Dec 07 2008

Status

approved