A253716 Hexagonal numbers (A000384) which are also centered heptagonal numbers (A069099).

1, 16322041, 4145734153, 67933251842771953, 17254778510170993681, 282742011610770921096804841, 71815357774355276244995175961, 1176788140728629029198108610250463201, 298899554649081431834808455098428958753, 4897858370145334123819452782766901335994312153

Offset: 1

Author

Colin Barker, Jan 10 2015

Keywords

• nonn
• easy

Examples

			16322041 is in the sequence because it is the 2857th hexagonal number and the 2160th centered heptagonal number.
		

Links

• Colin Barker, Table of n, a(n) for n = 1..208
• Index entries for linear recurrences with constant coefficients, signature (0,4162056194,0,-1).

Crossrefs

Cf. A000384, A069099, A253714, A253715.

Programs

Mathematica

LinearRecurrence[{0,4162056194,0,-1},{1,16322041,4145734153,67933251842771953},20] (* Harvey P. Dale, Jan 05 2017 *)

PARI

Vec(-x*(x-1)*(x^2+16322042*x+1)/((x^2-64514*x+1)*(x^2+64514*x+1)) + O(x^100))

Formula

a(n) = 4162056194*a(n-2)-a(n-4).

G.f.: -x*(x-1)*(x^2+16322042*x+1) / ((x^2-64514*x+1)*(x^2+64514*x+1)).