A259158 Positive triangular numbers (A000217) that are heptagonal numbers (A000566) divided by 2.

171, 355817826, 739874066553765, 1538466018777014327028, 3199027777735470191011289295, 6651936797966044301302839516949686, 13831784604089070782667939513452521937961, 28761287297921206463992005998270360082445758120

Offset

1,1

Links

Colin Barker, Table of n, a(n) for n = 1..158

Index entries for linear recurrences with constant coefficients, signature (2079363,-2079363,1).

Formula

G.f.: -171*x*(1443*x+1) / ((x-1)*(x^2-2079362*x+1)).

Example

171 is in the sequence because 171 is the 18th triangular number, and 2*171 is the 12th heptagonal number.

Mathematica

LinearRecurrence[{2079363, -2079363, 1}, {171, 355817826, 739874066553765}, 20] (* Vincenzo Librandi, Jun 20 2015 *)

Prog

(PARI) Vec(-171*x*(1443*x+1) / ((x-1)*(x^2-2079362*x+1)) + O(x^20))

Crossrefs

Cf. A000217, A000566, A259156, A259157, A259159-A259167.

Sequence in context: A097844 A076573 A015356 * A252139 A252132 A252131

Adjacent sequences: A259155 A259156 A259157 * A259159 A259160 A259161

Keyword

nonn,easy

Author

Colin Barker, Jun 19 2015

Status

approved