A123989 a(n) = H(2n)*(2n)!/n! where H(n) = sum{k=1 to n} 1/k, the n-th harmonic number.

0, 3, 25, 294, 4566, 88572, 2064504, 56243184, 1754322480, 61664980320, 2412077832000, 103928089910400, 4890979939104000, 249630539076979200, 13734482066534476800, 810355993296898406400, 51040766703826377676800

Offset

0,2

Links

Table of n, a(n) for n=0..16.

Mathematica

f[n_] := HarmonicNumber[2n](2n)!/n!; Table[f@n, {n, 0, 16}] - Robert G. Wilson v, Nov 26 2006

Crossrefs

Cf. A124078, A124079.

Sequence in context: A363354 A347255 A292111 * A001907 A212722 A236268

Adjacent sequences: A123986 A123987 A123988 * A123990 A123991 A123992

Keyword

easy,nonn

Author

Leroy Quet, Nov 23 2006

Extensions

More terms from Robert G. Wilson v, Nov 26 2006

Status

approved