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A074581 a(n)=T(3n+1), where T(n) are tribonacci numbers A000073. 2
0, 2, 13, 81, 504, 3136, 19513, 121415, 755476, 4700770, 29249425, 181997601, 1132436852, 7046319384, 43844049029, 272809183135, 1697490356184, 10562230626642, 65720971788709, 408933139743937, 2544489349890656 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..20.

FORMULA

a(n)=7a(n-1)-5a(n-2)+a(n-3), a(0)=0, a(1)=2, a(2)=13. G.f.: (2x-x^2)/(1-7x+5x^2-x^3).

MATHEMATICA

CoefficientList[Series[(2*x-x^2)/(1-7*x+5*x^2-x^3), {x, 0, 40}], x]

CROSSREFS

Cf. A000073.

Sequence in context: A189087 A037739 A037634 * A020059 A162772 A079752

Adjacent sequences:  A074578 A074579 A074580 * A074582 A074583 A074584

KEYWORD

easy,nonn

AUTHOR

Mario Catalani (mario.catalani(AT)unito.it), Aug 24 2002

EXTENSIONS

Definition corrected by David Scambler, Oct 18 2010

STATUS

approved

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Last modified August 16 11:20 EDT 2017. Contains 290623 sequences.