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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. 1
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 (list; graph; refs; listen; history; text; internal format)
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: A084928 A033683 A216284 * A030217 A030215 A098108

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

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Last modified November 18 02:54 EST 2017. Contains 294840 sequences.