A130638 a(n) = 1 iff d(n) = d(n+1), otherwise a(n)=0, where d(n) is the number of divisors of n, A000005.

0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0

Offset

1,1

Links

Antti Karttunen, Table of n, a(n) for n = 1..10000

Index entries for characteristic functions

Mathematica

Table[If[Length[Divisors[n]] == Length[Divisors[n + 1]], 1, 0], {n, 1, 80}] (* Stefan Steinerberger, Aug 12 2007 *)

Prog

(PARI) A130638(n) = (numdiv(n)==numdiv(n+1)); \\ Antti Karttunen, Oct 04 2017

Crossrefs

Characteristic function of A005237.

Cf. A000005.

Sequence in context: A216284 A360109 A355452 * A030217 A030215 A283020

Adjacent sequences: A130635 A130636 A130637 * A130639 A130640 A130641

Keyword

nonn

Author

Giovanni Teofilatto, Aug 11 2007

Extensions

Corrected and extended by Stefan Steinerberger, Aug 12 2007

More terms (up to a(105)) from Antti Karttunen, Oct 04 2017

Status

approved