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A259078 Heptagonal numbers (A000566) that are other heptagonal numbers divided by 2. 2
6426, 9875715583923, 15176968126834688342280, 23323916081375479417207129139097, 35844119643974208514403771705730853759974, 55085128439364942192092971212729781713850848998511, 84654649223375294035879228202426981713600292140166013136308 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Colin Barker, Table of n, a(n) for n = 1..109

Index entries for linear recurrences with constant coefficients, signature (1536796803,-1536796803,1).

FORMULA

G.f.: -189*x*(x^2+1372105*x+34) / ((x-1)*(x^2-1536796802*x+1)).

EXAMPLE

6426 is in the sequence because 6426 is the 51st heptagonal number, and 2*6426 is the 72nd heptagonal number.

MATHEMATICA

LinearRecurrence[{1536796803, -1536796803, 1}, {6426, 9875715583923, 15176968126834688342280}, 20] (* Harvey P. Dale, May 17 2018 *)

PROG

(PARI) Vec(-189*x*(x^2+1372105*x+34)/((x-1)*(x^2-1536796802*x+1)) + O(x^20))

CROSSREFS

Cf. A000566, A075528, A107736, A259079.

Sequence in context: A031578 A252612 A259060 * A104374 A222554 A104318

Adjacent sequences:  A259075 A259076 A259077 * A259079 A259080 A259081

KEYWORD

nonn,easy

AUTHOR

Colin Barker, Jun 18 2015

STATUS

approved

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Last modified December 12 15:11 EST 2019. Contains 329960 sequences. (Running on oeis4.)