A243220 Number of divisors of A002183(n).

1, 2, 2, 3, 4, 4, 3, 4, 6, 5, 6, 6, 8, 8, 6, 9, 8, 10, 12, 7, 12, 10, 12, 12, 12, 9, 12, 16, 8, 15, 12, 16, 18, 14, 12, 16, 12, 20, 9, 18, 14, 20, 24, 16, 15, 20, 14, 24, 24, 10, 21, 24, 16, 24, 30, 18, 18, 24, 16, 28, 30, 11, 24, 30, 18, 28, 36, 20, 21, 40, 28, 18, 32, 36, 12, 27, 36, 32, 42, 22, 48, 32, 20, 45, 36, 42, 13, 48, 30, 42, 60, 36, 48

Offset

1,2

Comments

No prime number > 17 is in this sequence. - J. Lowell, Feb 06 2022

References

S. Ramanujan, Collected Papers, Ed. G. H. Hardy et al., Cambridge 1927; Chelsea, NY, 1962, p. 87.

Links

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Formula

a(n) = A000005(A000005(A002182(n))). - Michel Marcus, Oct 08 2016

Mathematica

(* This program is not suitable to compute a large number of terms. *) Reap[For[record = 0; n = 1, n <= 10^9, n = If[n < 60, n + 1, n + 60], tau = DivisorSigma[0, n]; If[tau > record, record = tau; t = DivisorSigma[0, tau]; Print[t]; Sow[t]]]][[2, 1]] (* Jean-François Alcover, Oct 08 2016 *)

Crossrefs

Cf. A000005, A002183, A002182.

Sequence in context: A284009 A339695 A326846 * A334593 A293596 A301977

Adjacent sequences: A243217 A243218 A243219 * A243221 A243222 A243223

Keyword

nonn,look

Author

N. J. A. Sloane, Jun 01 2014

Status

approved