

A048921


9gonal heptagonal numbers (A000566).


2



1, 26884, 542041975, 10928650279834, 220343446399977901, 4442564555387704166896, 89570986345383445012986019, 1805930222253056462964119954950, 36411165051495138060899141518722649
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OFFSET

1,2


COMMENTS

As n increases, this sequence is approximately geometric with common ratio r = lim(n>Infinity,a(n)/a(n1)) = (6+sqrt(35))^4 = 10081+1704*sqrt(35).  Ant King, Dec 31 2011


LINKS

Table of n, a(n) for n=1..9.
Eric Weisstein's World of Mathematics, Nonagonal Heptagonal Number.


FORMULA

Contribution from Ant King, Dec 31 2011: (Start)
a(n) = 20163*a(n1)20163*a(n2)+a(n3).
a(n) = 20162*a(n1)a(n2)+6768.
a(n) = 1/560*((39+4*sqrt(35))*(6+sqrt(35))^(4*n3)+(394*sqrt(35))*(6sqrt(35))^(4*n3)188).
a(n) = floor(1/560*(39+4*sqrt(35))*(6+sqrt(35))^(4*n3)).
G.f.: x(1+6721*x+46*x^2) / ((1x)(120162*x+x^2)).
(End)


MATHEMATICA

LinearRecurrence[{20163, 20163, 1}, {1, 26884, 542041975}, 9]; (* Ant King, Dec 31 2011 *)


CROSSREFS

Cf. A048919, A048920.
Sequence in context: A235814 A199547 A051025 * A249496 A227348 A176359
Adjacent sequences: A048918 A048919 A048920 * A048922 A048923 A048924


KEYWORD

nonn


AUTHOR

Eric W. Weisstein


STATUS

approved



