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

1,2

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).

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)).

Example

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

Mathematica

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

Prog

(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))

Crossrefs

Cf. A000566, A003215, A254964, A254965.

Sequence in context: A269550 A238164 A112949 * A345455 A261806 A332147

Adjacent sequences: A254963 A254964 A254965 * A254967 A254968 A254969

Keyword

nonn,easy

Author

Colin Barker, Feb 11 2015

Status

approved