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A276823 a(n) = 3 * [3*n]_2! / ([2*n+1]_2! * [n+1]_2!), where [n]_q! is the q-factorial. 0
1, 9, 1241, 2634489, 87807053113, 46414431022602681, 390913823614809035461305, 52571422826552549403006580802745, 113007269646365312407427675894837602068665, 3884802624238339577626451297006421856376970743148729 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..10.

Eric Weisstein's World of Mathematics, q-Factorial, q-Binomial Coefficient.

FORMULA

a(n) ~ c * 2^((n-2)*(2*n+1)), where c = 3/QPochhammer(1/2, 1/2) = 3*A065446 = 3/A048651. - Vaclav Kotesovec, Sep 20 2016

MAPLE

a:= n-> 3*mul((2^j-1), j=1..3*n)/

         (mul((2^j-1), j=1..2*n+1)*

          mul((2^j-1), j=1..n+1)):

seq(a(n), n=1..12);  # Alois P. Heinz, Sep 20 2016

MATHEMATICA

Table[3 QFactorial[3 n, 2]/(QFactorial[2 n + 1, 2] QFactorial[n + 1, 2]), {n, 10}] (* or *)

Table[3 QBinomial[3 n, 2 n + 1, 2]/(1 - 3 * 2^n + 2^(2 n + 1)), {n, 10}]

CROSSREFS

Cf. A069777, A005329, A022166, A218449.

Sequence in context: A266602 A084149 A202981 * A020261 A266864 A076442

Adjacent sequences:  A276820 A276821 A276822 * A276824 A276825 A276826

KEYWORD

nonn

AUTHOR

Vladimir Reshetnikov, Sep 18 2016

STATUS

approved

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Last modified November 24 04:49 EST 2020. Contains 338607 sequences. (Running on oeis4.)