A117856 - OEIS

A117856

Number of palindromes of length n (in base 4).

3, 3, 12, 12, 48, 48, 192, 192, 768, 768, 3072, 3072, 12288, 12288, 49152, 49152, 196608, 196608, 786432, 786432, 3145728, 3145728, 12582912, 12582912, 50331648, 50331648, 201326592, 201326592, 805306368, 805306368, 3221225472, 3221225472, 12884901888

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OFFSET

1,1

LINKS

Table of n, a(n) for n=1..33.

Index entries for linear recurrences with constant coefficients, signature (0,4).

FORMULA

a(n) = 3*4^floor((n-1)/2).

From Colin Barker, Feb 15 2013: (Start)

a(n) = 4*a(n-2).

G.f.: -3*x*(x+1) / ((2*x-1)*(2*x+1)). (End)

MATHEMATICA