A254966 Heptagonal numbers (A000566) that are also centered hexagonal numbers (A003215).

1, 7, 469, 3367, 226051, 1622881, 108956107, 782225269, 52516617517, 377030956771, 25312900687081, 181728138938347, 12200765614555519, 87592585937326477, 5880743713315073071, 42219444693652423561, 2834506269052250664697, 20349684749754530829919

Offset: 1

Author

Colin Barker, Feb 11 2015

Keywords

• nonn
• easy

Examples

			469 is in the sequence because it is the 14th heptagonal number and the 13th centered hexagonal number.
		

Links

• Colin Barker, Table of n, a(n) for n = 1..746
• Index entries for linear recurrences with constant coefficients, signature (1,482,-482,-1,1).

Crossrefs

Cf. A000566, A003215, A254964, A254965.

Programs

Mathematica

LinearRecurrence[{1,482,-482,-1,1},{1,7,469,3367,226051},20] (* Harvey P. Dale, May 17 2019 *)

PARI

Vec(-x*(x^4+6*x^3-20*x^2+6*x+1)/((x-1)*(x^2-22*x+1)*(x^2+22*x+1)) + O(x^100))

Formula

a(n) = a(n-1)+482*a(n-2)-482*a(n-3)-a(n-4)+a(n-5).

G.f.: -x*(x^4+6*x^3-20*x^2+6*x+1) / ((x-1)*(x^2-22*x+1)*(x^2+22*x+1)).