A326998 - OEIS

A326998

a(n) = 1 + binomial(3*n-1, n) + binomial(3*n-1, n-1)*(binomial(2*n-1, n) + 1).

4, 5, 31, 365, 6271, 129130, 2877421, 66628441, 1578320767, 37983592076, 925196176906, 22754692780561, 564123212097901, 14079691134569845, 353428830512017081, 8915830309096530865, 225890912989184760703, 5744976464242932324976, 146603288011226858621356

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OFFSET

0,1

LINKS

Table of n, a(n) for n=0..18.

MAPLE

a := n -> 1 + binomial(3*n-1, n) + binomial(3*n-1, n-1)*(binomial(2*n-1, n) + 1):

seq(a(n), n=0..19);

CROSSREFS

Cf. A327001 (column 3). Essentially the same as A309725.

Sequence in context: A224219 A128867 A262031 * A270286 A271803 A269810

Adjacent sequences: A326995 A326996 A326997 * A326999 A327000 A327001

KEYWORD

nonn

AUTHOR

Peter Luschny, Aug 13 2019

STATUS

approved