A254230 Heptagonal numbers (A000566) which are also centered square numbers (A001844).

1, 4141, 85285, 429332905, 8842505113, 44514094237813, 916808615026525, 4615310318335580305, 95056550814337645681, 478524604381155542930941, 9855653300615347164456661, 49614388026831658683830230201, 1021853845419343873890857865865

Offset

1,2

Links

Colin Barker, Table of n, a(n) for n = 1..399

Index entries for linear recurrences with constant coefficients, signature (1,103682,-103682,-1,1).

Formula

a(n) = a(n-1)+103682*a(n-2)-103682*a(n-3)-a(n-4)+a(n-5).

G.f.: -x*(x^4+4140*x^3-22538*x^2+4140*x+1) / ((x-1)*(x^2-322*x+1)*(x^2+322*x+1)).

Example

4141 is in the sequence because it is the 41st heptagonal number and the 46th centered square number.

Prog

(PARI) Vec(-x*(x^4+4140*x^3-22538*x^2+4140*x+1)/((x-1)*(x^2-322*x+1)*(x^2+322*x+1)) + O(x^100))

Crossrefs

Cf. A000566, A001844, A254228, A254229.

Sequence in context: A255948 A273658 A107541 * A106537 A256080 A287514

Adjacent sequences: A254227 A254228 A254229 * A254231 A254232 A254233

Keyword

nonn,easy

Author

Colin Barker, Jan 27 2015

Status

approved