A242342 a(n) = binomial(n, smallest non-divisor of n).

0, 0, 3, 4, 10, 15, 21, 56, 36, 120, 55, 792, 78, 364, 105, 560, 136, 3060, 171, 1140, 210, 1540, 253, 42504, 300, 2600, 351, 3276, 406, 27405, 465, 4960, 528, 5984, 595, 376992, 666, 8436, 741, 9880, 820, 111930, 903, 13244, 990, 15180, 1081, 1712304, 1176

Offset: 1

Author

Reinhard Zumkeller, May 11 2014

Keywords

• nonn

Links

• Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A014105.

Programs

Haskell

a242342 n = if n <= 2 then 0 else a007318' n (a007978 n)

Mathematica

Join[{0,0},Table[Binomial[n,Complement[Range[DivisorSigma[0,n]], Divisors[ n]][[1]]],{n,3,50}]] (* Harvey P. Dale, May 23 2019 *)

Formula

a(n) = A007318(n, A007978(n)) for n > 2.

a(2*n-1) = A014105(n).