

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
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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(n1)+322*a(n2)322*a(n3)a(n4)+a(n5).
G.f.: x*(45*x^3+161*x^245*x1) / ((x1)*(x^218*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^245*x1)/((x1)*(x^218*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



