



1260, 5148, 11628, 20700, 32364, 46620, 63468, 82908, 104940, 129564, 156780, 186588, 218988, 253980, 291564, 331740, 374508, 419868, 467820, 518364, 571500, 627228, 685548, 746460, 809964, 876060, 944748, 1016028, 1089900, 1166364
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OFFSET

1,1


COMMENTS

The identity (72*n^21)^2(1296*n^236)*(2*n)^2 = 1 can be written as A158738(n)^2a(n)*A005843(n)^2 = 1.


LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..10000
Vincenzo Librandi, X^2AY^2=1
Index to sequences with linear recurrences with constant coefficients, signature (3,3,1).


FORMULA

G.f.: 36*x*(3538*x+x^2)/(x1)^3.
a(n) = 3*a(n1) 3*a(n2) +a(n3).


MATHEMATICA

LinearRecurrence[{3, 3, 1}, {1260, 5148, 11628}, 50] (* Vincenzo Librandi, Feb 20 2012 *)


PROG

(MAGMA) I:=[1260, 5148, 11628]; [n le 3 select I[n] else 3*Self(n1)3*Self(n2)+1*Self(n3): n in [1..40]]; // Vincenzo Librandi, Feb 20 2012
(PARI) for(n=1, 40, print1(1296*n^2  36", ")); \\ Vincenzo Librandi, Feb 20 2012


CROSSREFS

Cf. A005843, A158738.
Sequence in context: A144563 A175746 A179690 * A252277 A203402 A047634
Adjacent sequences: A158734 A158735 A158736 * A158738 A158739 A158740


KEYWORD

nonn,easy


AUTHOR

Vincenzo Librandi, Mar 25 2009


EXTENSIONS

Comment rewritten and formula replaced by R. J. Mathar, Oct 22 2009


STATUS

approved



