A068905 Binomial(sigma(n),omega(n)), where sigma(n) is the sum of divisors of n (A000203) and omega the number of distinct prime factors (A001221).

1, 3, 4, 7, 6, 66, 8, 15, 13, 153, 12, 378, 14, 276, 276, 31, 18, 741, 20, 861, 496, 630, 24, 1770, 31, 861, 40, 1540, 30, 59640, 32, 63, 1128, 1431, 1128, 4095, 38, 1770, 1540, 4005, 42, 142880, 44, 3486, 3003, 2556, 48, 7626

Offset: 1

Author

Reinhard Zumkeller, Mar 06 2002

Keywords

• nonn

Links

• G. C. Greubel, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A068903, A068904.

Programs

Mathematica

Binomial[DivisorSigma[1,#],Length[FactorInteger[#]]]&/@Range[50]  (* Harvey P. Dale, Feb 18 2011 *)

PARI

a(n)=binomial(sigma(n),omega(n)) \\ Charles R Greathouse IV, Feb 19 2013