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A292540 Number of 3-cycles in the n-Sierpinski tetrahedron graph. 3
4, 20, 80, 320, 1280, 5120, 20480, 81920, 327680, 1310720, 5242880, 20971520, 83886080, 335544320, 1342177280, 5368709120, 21474836480, 85899345920, 343597383680, 1374389534720, 5497558138880, 21990232555520, 87960930222080, 351843720888320, 1407374883553280 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..25.

Eric Weisstein's World of Mathematics, Graph Cycle

Eric Weisstein's World of Mathematics, Sierpinski Tetrahedron Graph

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

FORMULA

a(n) = 5*4^(n - 1) for n > 1.

a(n) = 4*a(n-1) for n > 2.

G.f. -4*x*(1 + x)/(-1 + 4 x).

MATHEMATICA

Table[If[n == 1, 4, 5 4^(n - 1)], {n, 10}]

Join[{4}, LinearRecurrence[{4}, {20}, 30]]

CoefficientList[Series[-((4 (1 + x))/(-1 + 4 x)), {x, 0, 20}], x]

CROSSREFS

Cf. A003947, A269696.

Cf. A292542 (4-cycles), A292543 (5-cycles), A292545 (6-cycles).

Sequence in context: A082138 A074358 A255050 * A320934 A055296 A140532

Adjacent sequences:  A292537 A292538 A292539 * A292541 A292542 A292543

KEYWORD

nonn

AUTHOR

Eric W. Weisstein, Sep 18 2017

STATUS

approved

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Last modified April 18 06:48 EDT 2019. Contains 322209 sequences. (Running on oeis4.)