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A026121 3^n*(3^n-1)/2. 4
0, 3, 36, 351, 3240, 29403, 265356, 2390391, 21520080, 193700403, 1743362676, 15690441231, 141214502520, 1270932117003, 11438393835996, 102945558872871, 926510072902560, 8338590785263203, 75047317454789316, 675425858255365311 (list; graph; refs; listen; history; internal format)
OFFSET

0,2

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..200

FORMULA

a(n)=C(3^n,2),n>=0. - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jan 07 2008

MAPLE

seq(binomial(3^n, 2), n=0..19); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jan 07 2008

PROG

(MAGMA) [3^n*(3^n-1)/2: n in [0..30]]; // Vincenzo Librandi, May 01 2011

CROSSREFS

Sequence in context: A038146 A067444 A092648 * A055303 A068177 A099670

Adjacent sequences:  A026118 A026119 A026120 * A026122 A026123 A026124

KEYWORD

nonn

AUTHOR

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

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Last modified February 17 16:00 EST 2012. Contains 206050 sequences.