A062068 a(n) = d(sigma(n)), where d(k) is the number of divisors function (A000005) and sigma(k) is the sum of divisor function (A000203).

1, 2, 3, 2, 4, 6, 4, 4, 2, 6, 6, 6, 4, 8, 8, 2, 6, 4, 6, 8, 6, 9, 8, 12, 2, 8, 8, 8, 8, 12, 6, 6, 10, 8, 10, 4, 4, 12, 8, 12, 8, 12, 6, 12, 8, 12, 10, 6, 4, 4, 12, 6, 8, 16, 12, 16, 10, 12, 12, 16, 4, 12, 8, 2, 12, 15, 6, 12, 12, 15, 12, 8, 4, 8, 6, 12, 12, 16, 10, 8, 3, 12, 12, 12, 12, 12

Offset: 1

Author

Amarnath Murthy, Jun 13 2001

Keywords

• nonn
• easy

Examples

			a(5) = d(sigma(5)) = d(6) = 4.
		

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..1000 from Harry J. Smith)

Crossrefs

Cf. A000005, A000203, A062068, A062069.

Programs

Mathematica

Table[DivisorSigma[0, DivisorSigma[1, n]], {n, 1, 80}] (* Carl Najafi, Aug 16 2011 *)

PARI

for(n=1,120,print(numdiv(sigma(n))))

PARI

{ for (n=1, 1000, write("b062068.txt", n, " ", numdiv(sigma(n))) ) } \\ Harry J. Smith, Jul 31 2009

Formula

a(n) = A000005(A000203(n)) = A062069(n) + A076360(n). - Amiram Eldar, Mar 16 2025

Extensions

Corrected and extended by Jason Earls, Jun 16 2001