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A254230 Heptagonal numbers (A000566) which are also centered square numbers (A001844). 3
1, 4141, 85285, 429332905, 8842505113, 44514094237813, 916808615026525, 4615310318335580305, 95056550814337645681, 478524604381155542930941, 9855653300615347164456661, 49614388026831658683830230201, 1021853845419343873890857865865 (list; graph; refs; listen; history; text; internal format)
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

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Last modified September 27 10:28 EDT 2021. Contains 347689 sequences. (Running on oeis4.)