A253579 Centered pentagonal numbers (A005891) which are also centered octagonal numbers (A016754).

1, 22801, 1666681, 47411143081, 3465632747641, 98584929298781641, 7206305041398228481, 204993755756525779060081, 14984516863488437537571601, 426256225957302372068628976801, 31158234954289838149958560780201, 886340998518823181233611960679431001

Offset: 1

Author

Colin Barker, Jan 04 2015

Keywords

• nonn
• easy

Examples

			22801 is in the sequence because it is the 96th centered pentagonal number and the 76th centered octagonal number.
		

Links

• Colin Barker, Table of n, a(n) for n = 1..317
• Index entries for linear recurrences with constant coefficients, signature (1,2079362,-2079362,-1,1).

Crossrefs

Cf. A005891, A016754, A253410, A253411.

Programs

PARI

Vec(-x*(x^4+22800*x^3-435482*x^2+22800*x+1)/((x-1)*(x^2-1442*x+1)*(x^2+1442*x+1)) + O(x^100))

Formula

a(n) = a(n-1)+2079362*a(n-2)-2079362*a(n-3)-a(n-4)+a(n-5).

G.f.: -x*(x^4+22800*x^3-435482*x^2+22800*x+1) / ((x-1)*(x^2-1442*x+1)*(x^2+1442*x+1)).