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A065559 Smallest k such that tau(n+k) = tau(k). 5
2, 3, 2, 3, 2, 5, 8, 3, 2, 3, 2, 5, 8, 3, 2, 3, 2, 5, 8, 3, 2, 7, 10, 5, 8, 3, 2, 3, 2, 7, 8, 5, 6, 3, 2, 5, 14, 3, 2, 3, 2, 5, 8, 3, 2, 7, 8, 5, 6, 3, 2, 6, 21, 5, 10, 3, 2, 3, 2, 7, 8, 5, 6, 3, 2, 5, 10, 3, 2, 3, 2, 7, 14, 5, 10, 3, 2, 5, 6, 3, 2, 7, 8, 5, 6, 3, 2, 6, 6, 7, 15, 5, 22, 3, 2, 5, 14, 3, 2 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Harry J. Smith, Table of n, a(n) for n = 1..1000

Eric W. Weisstein, MathWorld: Divisor Function

MAPLE

with(numtheory):

a:= proc(n) local k; for k while tau(n+k)<>tau(k) do od; k end:

seq(a(n), n=1..120);  # Alois P. Heinz, Mar 18 2013

MATHEMATICA

tau[m_] := DivisorSigma[0, m]; a[n_] := Catch[ For[k = 1, True, k++, If[ tau[n+k] == tau[k], Throw[k]]]]; Table[a[n], {n, 1, 99}] (* Jean-Fran├žois Alcover, Mar 18 2013 *)

skt[n_]:=Module[{k=1}, While[DivisorSigma[0, k]!=DivisorSigma[0, n+k], k++]; k]; Array[skt, 100] (* Harvey P. Dale, Oct 13 2017 *)

PROG

(PARI): tau(m) = {local(k, n); for(k=1, m, n=1; while(numdiv(n)!=numdiv(n+k), n++); print1(n, ", "))} tau(200)

(PARI) { for (n=1, 1000, k=1; while(numdiv(n + k) != numdiv(k), k++); write("b065559.txt", n, " ", k) ) } \\ Harry J. Smith, Oct 22 2009

CROSSREFS

Cf. A000005.

Sequence in context: A282691 A265577 A251103 * A087317 A086489 A015886

Adjacent sequences:  A065556 A065557 A065558 * A065560 A065561 A065562

KEYWORD

nonn

AUTHOR

Jason Earls, Nov 29 2001

STATUS

approved

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Last modified February 23 18:54 EST 2019. Contains 320438 sequences. (Running on oeis4.)