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A254229 Indices of centered square numbers (A001844) which are also heptagonal numbers (A000566). 3
1, 46, 207, 14652, 66493, 4717738, 21410379, 1519096824, 6894075385, 489144459430, 2219870863431, 157502996839476, 714791523949237, 50715475837851682, 230160650840790723, 16330225716791401968, 74111014779210663409, 5258281965330993581854 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Also positive integers y in the solutions to 5*x^2 - 4*y^2 - 3*x + 4*y - 2 = 0, the corresponding values of x being A254228.

LINKS

Colin Barker, Table of n, a(n) for n = 1..797

Index entries for linear recurrences with constant coefficients, signature (1,322,-322,-1,1).

FORMULA

a(n) = a(n-1)+322*a(n-2)-322*a(n-3)-a(n-4)+a(n-5).

G.f.: x*(45*x^3+161*x^2-45*x-1) / ((x-1)*(x^2-18*x+1)*(x^2+18*x+1)).

EXAMPLE

46 is in the sequence because the 46th centered square number is 4141, which is also the 41st heptagonal number.

PROG

(PARI) Vec(x*(45*x^3+161*x^2-45*x-1)/((x-1)*(x^2-18*x+1)*(x^2+18*x+1)) + O(x^100))

CROSSREFS

Cf. A000566, A001844, A254228, A254230.

Sequence in context: A160334 A235550 A083358 * A234161 A234154 A251410

Adjacent sequences:  A254226 A254227 A254228 * A254230 A254231 A254232

KEYWORD

nonn,easy

AUTHOR

Colin Barker, Jan 27 2015

STATUS

approved

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Last modified August 4 05:02 EDT 2021. Contains 346442 sequences. (Running on oeis4.)