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A236967

Expansion of (1+3*x)^2/(1-3*x)^2.

1, 12, 72, 324, 1296, 4860, 17496, 61236, 209952, 708588, 2361960, 7794468, 25509168, 82904796, 267846264, 860934420, 2754990144, 8781531084, 27894275208, 88331871492, 278942752080, 878669669052, 2761533245592, 8661172452084, 27113235502176, 84728860944300

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OFFSET

0,2

LINKS

Table of n, a(n) for n=0..25.

Index entries for linear recurrences with constant coefficients, signature (6,-9)

FORMULA

For n >= 1, a(n) = 4*n*3^n. - Robert Israel, May 08 2014

PROG

(Magma) m:=30; R<x>:=PowerSeriesRing(Integers(), m); Coefficients(R!((1+3*x)^2/(1-3*x)^2));

CROSSREFS

Cf. Expansion of (1 + k*x)^m/(1 - k*x)^m where the values of k,m are: