A246908 a(n) = sigma(n + sigma(n)) - sigma(n).

2, 3, 4, 5, 6, 27, 16, 9, 23, 38, 12, 62, 26, 36, 32, 17, 30, 41, 36, 54, 22, 54, 24, 164, 89, 84, 28, 168, 30, 144, 72, 57, 73, 126, 36, 37, 86, 111, 64, 162, 42, 192, 76, 171, 90, 108, 72, 184, 105, 75, 96, 274, 54, 240, 56, 252, 58, 176, 84, 392, 106, 144

Offset: 1

Author

Jaroslav Krizek, Sep 07 2014

Keywords

• nonn

Examples

			For n = 6; a(n) = sigma(6 + sigma(6)) - sigma(6) = sigma(18) - sigma(6) = 39 - 12 = 27.
		

Links

• Ivan Neretin, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000203, A078762, A246456.

Programs

Magma

[SumOfDivisors(n+SumOfDivisors(n))-SumOfDivisors(n):n in[1..1000]]

Mathematica

sig[n_]:=Module[{d6=DivisorSigma[1,n]},DivisorSigma[1,n+d6]-d6]; Array[ sig,70] (* Harvey P. Dale, Feb 20 2015 *)

PARI

vector(100,n,sigma(n+sigma(n))-sigma(n)) \\ Derek Orr, Sep 07 2014

Formula

a(n) = n + 1 for number in A078762 (numbers n such that n + sigma(n) is prime).