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

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

Offset

1,1

Links

Colin Barker, Table of n, a(n) for n = 1..200

Index entries for linear recurrences with constant coefficients, signature (103683,-103683,1).

Formula

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

Example

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

Mathematica

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

Prog

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

Crossrefs

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

Sequence in context: A013850 A174001 A273234 * A340181 A131678 A229687

Adjacent sequences: A259156 A259157 A259158 * A259160 A259161 A259162

Keyword

nonn,easy

Author

Colin Barker, Jun 19 2015

Status

approved