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

1,2

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).

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)).

Example

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

Prog

(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))

Crossrefs

Cf. A005891, A016754, A253410, A253411.

Sequence in context: A254087 A254094 A203065 * A197319 A263215 A263212

Adjacent sequences: A253576 A253577 A253578 * A253580 A253581 A253582

Keyword

nonn,easy

Author

Colin Barker, Jan 04 2015

Status

approved