A259159 Positive squares (A000290) that are heptagonal numbers (A000566) divided by 2.

9, 938961, 97353360225, 10093791093915321, 1046544448101974957529, 108507821458015176452612289, 11250307943363385076857772396401, 1166454428075294670080752381151042025, 120940328000452394039949183305644566845481

Offset: 1

Author

Colin Barker, Jun 19 2015

Keywords

• nonn
• easy

Examples

			9 is in the sequence because 9 is the 3rd square, and 2*9 is the 3rd heptagonal number.
		

Links

• Colin Barker, Table of n, a(n) for n = 1..200
• Index entries for linear recurrences with constant coefficients, signature (103683,-103683,1).

Crossrefs

Cf. A000290, A000566, A259156-A259158, A259160-A259167.

Programs

Mathematica

LinearRecurrence[{103683, -103683, 1},{9, 938961, 97353360225}, 20] (* Vincenzo Librandi, Jun 20 2015 *)

PARI

Vec(-9*x*(x^2+646*x+1)/((x-1)*(x^2-103682*x+1)) + O(x^20))

Formula

G.f.: -9*x*(x^2+646*x+1) / ((x-1)*(x^2-103682*x+1)).