A273353 Number of divisors of A067128(n).

1, 2, 2, 3, 4, 4, 4, 6, 6, 6, 8, 8, 9, 10, 12, 12, 12, 12, 12, 12, 16, 16, 18, 20, 20, 24, 24, 24, 24, 24, 24, 24, 24, 24, 30, 32, 32, 36, 36, 40, 40, 48, 48, 48, 48, 48, 48, 48, 48, 60, 64, 64, 72, 72, 72, 80, 80, 84, 90, 96, 96, 96, 96, 96, 96, 96, 96, 96, 100, 108, 120, 120, 120, 128, 128, 144, 144, 144, 144, 144, 160

Offset: 1

Author

David A. Corneth, May 20 2016

Keywords

• nonn

Comments

Is a(n + 1) / a(n) ~ 1 for large n?

Every term in this sequence also appears in A002183, where every element of this sequence occurs exactly once.

In A067128 it is asked if A034287 = A067128. If that is the case then this sequence is also the number of divisors of A034287.

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000005, A002182, A002183, A034287, A067128.

Programs

Mathematica

s = {}; dmax = 0; Do[d = DivisorSigma[0, n]; If[d >= dmax, AppendTo[s, d]; dmax = d], {n, 1, 10^6}]; s (* Amiram Eldar, Jun 07 2019 *)

PARI

is_a067128(n) = my(nd=numdiv(n)); for(k=1, n-1, if(numdiv(k) > nd, return(0))); return(1)
for(n=1, 50000, if(is_a067128(n), print1(numdiv(n), ", "))) \\ Felix Fröhlich, May 24 2016

Formula

a(n) = A000005(A067128(n)).