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A025551 3^n*(3^n+1)/2. 2
1, 6, 45, 378, 3321, 29646, 266085, 2392578, 21526641, 193720086, 1743421725, 15690618378, 141215033961, 1270933711326, 11438398618965, 102945573221778, 926510115949281, 8338590914403366, 75047317842209805, 675425859417626778 (list; graph; refs; listen; history; internal format)
OFFSET

0,2

FORMULA

Binomial transform of A081342, 6th binomial transform of (1, 0, 9, 0, 81, 0, 729, 0, . . ), inverse binomial transform of A081343; a(n) = 12a(n-1) - 27a(n-2), a(0) = 1, a(1) = 6; G.f.: = (1-6x)/((1-3x)(1-9x)); E.g.f.: exp(7x)cosh(3x) . - Philippe DELEHAM (kolotoko(AT)wanadoo.fr), Jul 11 2005

((6+sqrt9)^n+(6-sqrt9)^n)/2 [From Al Hakanson (hawkuu(AT)gmail.com), Dec 08 2008]

CROSSREFS

Sequence in context: A007193 A153399 A007194 * A101600 A135148 A137974

Adjacent sequences:  A025548 A025549 A025550 * A025552 A025553 A025554

KEYWORD

nonn

AUTHOR

N. J. A. Sloane (njas(AT)research.att.com).

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Last modified February 15 19:15 EST 2012. Contains 205852 sequences.