A138113 -id:A138113 - cp's OEIS frontend

A140410 Number of divisors of A138113(n).

1, 2, 4, 8, 16, 30, 60, 96, 160, 288, 432, 768, 1152, 2016, 3584, 5632, 8448, 13824, 20736, 33792, 63360, 103680, 155520, 248832, 414720, 691200, 1105920, 1802240, 2703360, 4423680, 6635520, 10321920, 16515072, 27869184, 46448640

Offset: 1

J. Lowell, Jun 16 2008

nonn

Cf. A138113.

More terms from Max Alekseyev, Jan 31 2012

A140635 Smallest positive integer having the same number of divisors as n.

Original entry on oeis.org

1, 2, 2, 4, 2, 6, 2, 6, 4, 6, 2, 12, 2, 6, 6, 16, 2, 12, 2, 12, 6, 6, 2, 24, 4, 6, 6, 12, 2, 24, 2, 12, 6, 6, 6, 36, 2, 6, 6, 24, 2, 24, 2, 12, 12, 6, 2, 48, 4, 12, 6, 12, 2, 24, 6, 24, 6, 6, 2, 60, 2, 6, 12, 64, 6, 24, 2, 12, 6, 24, 2, 60, 2, 6, 12, 12, 6, 24, 2, 48, 16, 6, 2, 60, 6, 6, 6, 24, 2

Offset: 1

Max Alekseyev, May 19 2008

nonn

a(n) <= n for all n. Moreover, a(n) = n if and only if n belongs to A005179 or A007416.

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

Cf. A000005, A005179, A007416, A139770.

Cf. A019505, A138113, A061300 (sequences that can be defined in terms of this sequence).

a140635[n_] := NestWhile[#+1&, 1, DivisorSigma[0, n]!=DivisorSigma[0, #]&]
a140635[{m_, n_}] := Map[a140635, Range[m, n]]
a140635[{1, 89}] (* Hartmut F. W. Hoft, Jun 13 2023 *)

A140635(n) = { my(nd = numdiv(n)); for (i=1, n, if (numdiv(i) == nd, return (i))); }; \\ After A139770, Antti Karttunen, May 27 2017

from sympy import divisor_count as d
def a(n):
    x=d(n)
    m=1
    while True:
        if d(m)==x: return m
        else: m+=1 # Indranil Ghosh, May 27 2017

a(n) = A005179(A000005(n)).

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A140410 Number of divisors of A138113(n).

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A140635 Smallest positive integer having the same number of divisors as n.

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