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A071854 a(n) = (number of distinct prime factors in C(2n,n)) - pi(n). 1
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 (list; graph; refs; listen; history; text; internal format)
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: A274354 A083870 A052299 * A183025 A072410 A342824

Adjacent sequences:  A071851 A071852 A071853 * A071855 A071856 A071857

KEYWORD

nonn

AUTHOR

Benoit Cloitre, Jun 09 2002

STATUS

approved

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Last modified May 9 19:28 EDT 2021. Contains 343746 sequences. (Running on oeis4.)