A171937 Forward van Eck transform of A000005.

0, 1, 2, 5, 2, 2, 4, 2, 16, 4, 2, 6, 4, 1, 6, 65, 2, 2, 4, 8, 1, 4, 6, 6, 24, 1, 6, 4, 2, 10, 6, 12, 1, 1, 3, 64, 4, 1, 7, 2, 2, 12, 4, 1, 5, 5, 6, 32, 72, 2, 4, 11, 6, 2, 2, 10, 1, 4, 2, 12, 6, 3, 5, 665, 4, 4, 4, 7, 5, 8, 2, 12, 6, 3, 1, 16, 5, 10, 4, 32, 544, 3, 6, 6, 1, 1, 4, 14, 8, 6, 2, 6, 1, 1, 11

Offset: 1

Author

N. J. A. Sloane, Oct 24 2010

Keywords

• nonn

Comments

Least positive k such that d(n) = d(n+k), or 0 if no such k exists (d = A000005). - Altug Alkan, Jul 29 2016

Links

• Michael De Vlieger, Table of n, a(n) for n = 1..10001
• N. J. A. Sloane, Transforms

Crossrefs

Cf. A000005, A171936.

Cf. A079427.

Programs

Mathematica

{0}~Join~Array[Block[{k = 1}, While[DivisorSigma[0, #] != DivisorSigma[0, # + k], k++]; k] &, 94, 2] (* Michael De Vlieger, Aug 19 2021 *)

PARI

a(n) = if (n==1, 0, my(m=1, nd=numdiv(n)); while(numdiv(n+m) != nd, m++); m); \\ Michel Marcus, Sep 14 2021

Formula

a(n) = A079427(n) - n. - Ridouane Oudra, Sep 14 2021