A067437 Number of distinct prime factors in binomial(2*n,n)+1.

1, 1, 2, 1, 2, 2, 1, 2, 3, 2, 2, 1, 2, 3, 3, 4, 2, 2, 1, 2, 4, 1, 3, 2, 4, 4, 3, 4, 3, 2, 3, 2, 2, 2, 5, 4, 3, 1, 4, 3, 2, 3, 2, 4, 2, 1, 3, 3, 4, 2, 6, 3, 7, 5, 4, 5, 3, 3, 2, 3, 5, 1, 5, 2, 3, 4, 3, 1, 6, 6, 3, 1, 3, 2, 5, 2, 4, 4, 4, 2, 6, 2, 2, 1, 3, 4, 3, 2, 4, 3

Offset: 1

Author

Benoit Cloitre, Feb 23 2002

Keywords

• easy
• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..212

Crossrefs

Cf. A001221, A000984, A067434, A244174.

Programs

Mathematica

a[n_] := PrimeNu[Binomial[2*n,n] + 1]; Array[a,90] (* Amiram Eldar, Apr 23 2022 *)

Formula

a(n) = A001221(A244174(n)). - Amiram Eldar, Apr 23 2022