A071854 a(n) = (number of distinct prime factors in C(2n,n)) - pi(n).

1, 1, 0, 1, 0, 1, 0, 1, 1, 1, 1, 1, 0, 0, 1, 2, 1, 2, 1, 2, 2, 2, 0, 1, 1, 1, 1, 3, 3, 2, 1, 2, 3, 3, 3, 3, 2, 3, 2, 3, 2, 3, 2, 2, 3, 3, 2, 3, 3, 3, 3, 3, 3, 4, 3, 3, 3, 4, 3, 4, 3, 3, 3, 4, 4, 5, 5, 4, 4, 4, 3, 4, 3, 3, 4, 4, 5, 5, 4, 5, 5, 5, 4, 4, 4, 5, 5, 5, 4, 4, 5, 6, 5, 5, 5, 6, 5, 4, 5, 6, 5, 6, 5, 6, 6

Offset

1,16

Links

T. D. Noe, Table of n, a(n) for n=1..1000

Formula

a(n) = A067434(n) - A000720(n)

Prog

(PARI) for(n=1, 200, print1(omega(binomial(2*n, n))-sum(i=1, n, isprime(i)), ", "))

Crossrefs

Sequence in context: A083870 A368779 A052299 * A183025 A072410 A342824

Adjacent sequences: A071851 A071852 A071853 * A071855 A071856 A071857

Keyword

nonn

Author

Benoit Cloitre, Jun 09 2002

Status

approved