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A096019 a(0)=3, a(n) = 3*a(n-1) + 2*(-1)^n. 1
3, 7, 23, 67, 203, 607, 1823, 5467, 16403, 49207, 147623, 442867, 1328603, 3985807, 11957423, 35872267, 107616803, 322850407, 968551223, 2905653667, 8716961003, 26150883007, 78452649023, 235357947067, 706073841203, 2118221523607 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

The number of Pythagorean quadruples mod 3^n is given by a(n) 3^(2n-1). See A096018.

LINKS

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

Index entries for linear recurrences with constant coefficients, signature (2, 3).

FORMULA

a(n) = 3^(n+1)-(3^n-(-1)^n)/2.

a(n) = 2*a(n-1)+3*a(n-2). G.f.: (3+x)/((1+x)*(1-3*x)). [Colin Barker, Mar 26 2012]

CROSSREFS

Sequence in context: A148692 A201204 A106964 * A148693 A148694 A148695

Adjacent sequences:  A096016 A096017 A096018 * A096020 A096021 A096022

KEYWORD

nonn,easy

AUTHOR

T. D. Noe, Jun 15 2004

STATUS

approved

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Last modified July 23 22:20 EDT 2021. Contains 346265 sequences. (Running on oeis4.)