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A161576 a(1)=1. a(n) = the smallest integer > a(n-1) such that d(a(n)) > d(n), where d(n) = the number of divisors of n. 3
1, 4, 6, 8, 9, 12, 14, 16, 18, 20, 21, 24, 25, 28, 30, 32, 33, 36, 38, 40, 42, 44, 45, 48, 50, 52, 54, 56, 57, 60, 62, 64, 66, 68, 70, 72, 74, 75, 76, 80, 81, 84, 85, 88, 90, 92, 93, 96, 98, 100, 102, 104, 105, 108, 110, 112, 114, 116, 117, 120, 121, 124, 126, 128, 130, 132 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..1000

MAPLE

with(numtheory): a := proc (n) local j: if n = 1 then 1 else for j from a(n-1)+1 while tau(j) <= tau(n) do end do: j end if end proc: seq(a(n), n = 1 .. 70); # Emeric Deutsch, Jul 11 2009

MATHEMATICA

si[{n_, a_}]:=Module[{k=a+1, d=DivisorSigma[0, n+1]}, While[DivisorSigma[0, k]<=d, k++]; {n+1, k}]; NestList[si, {1, 1}, 70][[All, 2]] (* Harvey P. Dale, Nov 12 2017 *)

CROSSREFS

Cf. A137518, A161577, A161578.

Sequence in context: A231573 A327204 A047409 * A327446 A100425 A258614

Adjacent sequences:  A161573 A161574 A161575 * A161577 A161578 A161579

KEYWORD

nonn

AUTHOR

Leroy Quet, Jun 14 2009

EXTENSIONS

Extended by Emeric Deutsch, Jul 11 2009

STATUS

approved

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Last modified January 28 03:20 EST 2022. Contains 350654 sequences. (Running on oeis4.)