A276679 Number of divisors of the n-th hexagonal number.

1, 4, 4, 6, 6, 8, 4, 16, 6, 8, 8, 12, 6, 16, 8, 10, 8, 24, 4, 24, 8, 8, 12, 16, 9, 16, 8, 24, 8, 16, 4, 36, 16, 8, 16, 18, 4, 24, 16, 16, 10, 16, 8, 24, 12, 16, 8, 40, 6, 36, 8, 12, 16, 16, 8, 32, 8, 16, 12, 48, 6, 16, 24, 14, 16, 16, 8, 48, 8, 16, 8, 48, 8

Offset: 1

Author

Colin Barker, Sep 13 2016

Keywords

• nonn

Examples

			a(6) = 8 because the 6th hexagonal number is 66, which has 8 divisors: 1,2,3,6,11,22,33,66.
		

Links

• Colin Barker, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A000005, A000384.

Number of divisors of m-gonal numbers (m = 3..10): A063440, A048691, A276678, this sequence, A276680, A276681, A276682, A276683.

Programs

PARI

pg(m, n) = (n^2*(m-2)-n*(m-4))/2 \\ n-th m-gonal number
vector(100, n, numdiv(pg(6,n)))

Formula

a(n) = A000005(A000384(n)). - Omar E. Pol, Sep 13 2016