A126786 a(n) = n-th positive divisor of ((2n)!/n!^2).

1, 2, 4, 7, 6, 7, 11, 11, 20, 34, 17, 34, 25, 19, 19, 34, 27, 25, 25, 26, 33, 41, 36, 45, 47, 49, 98, 62, 40, 86, 88, 82, 57, 65, 67, 148, 142, 67, 92, 134, 61, 66, 56, 68, 71, 68, 63, 71, 83, 97, 106, 134, 77, 95, 166, 186, 222, 183, 113, 119, 103, 103, 107, 178, 134, 164

Offset

1,2

Links

David A. Corneth, Table of n, a(n) for n = 1..10000

Example

(2*5)!/5!^2 = 252. The divisors of 252 are 1, 2, 3, 4, 6, 7, 9, 12, 14, 18, 21, 28, 36, 42, 63, 84, 126, 252. The 5th of these is 6. So a(5) = 6.

Mathematica

f[n_] := Divisors[(2n)!/n!^2][[n]]; Array[f, 66] (* Ray Chandler, Feb 26 2007 *)

Crossrefs

Cf. A000984.

Sequence in context: A335818 A129980 A198137 * A154614 A342616 A161211

Adjacent sequences: A126783 A126784 A126785 * A126787 A126788 A126789

Keyword

nonn

Author

Leroy Quet, Feb 18 2007

Extensions

Extended by Ray Chandler, Feb 26 2007

More terms from Emeric Deutsch, Feb 25 2007

Status

approved