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A080405
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Number of distinct primes dividing n-th Catalan number.
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5
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0, 0, 1, 1, 2, 3, 3, 3, 4, 4, 4, 5, 5, 5, 6, 6, 7, 8, 8, 9, 9, 9, 9, 9, 9, 9, 9, 10, 11, 11, 11, 11, 12, 13, 13, 13, 13, 13, 13, 14, 14, 15, 15, 15, 16, 16, 16, 17, 17, 17, 17, 17, 17, 19, 18, 18, 18, 18, 19, 19, 20, 20, 20, 20, 21, 22, 22, 23, 22, 22, 22, 23, 23, 23, 24, 24, 25, 25
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OFFSET
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0,5
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LINKS
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Enrique Pérez Herrero, Table of n, a(n) for n = 0..3000
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FORMULA
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a(n) = A001221(A000108(n)).
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EXAMPLE
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a(5) = 3, as C(5) = 42 factors as 2*3*7 (3 distinct prime factors).
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MATHEMATICA
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PrimeNu[CatalanNumber[Range[0, 80]]] (* Harvey P. Dale, Mar 27 2013 *)
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PROG
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(PARI) C(n)=binomial(2*n, n)/(n+1);
for(n=1, 100, print1(matsize(factor(C(n-1)))[1], ", ")); \\ Joerg Arndt, Apr 19 2014
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CROSSREFS
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Cf. A001221, A000108.
Cf. A081399.
Sequence in context: A196176 A121536 A285761 * A039728 A332965 A334220
Adjacent sequences: A080402 A080403 A080404 * A080406 A080407 A080408
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KEYWORD
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nonn
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AUTHOR
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Labos Elemer, Mar 19 2003
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STATUS
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approved
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