OFFSET
1,2
COMMENTS
a(A071853(n)) = 0.
LINKS
Olivier GĂ©rard, Table of n, a(n) for n = 1..1000
EXAMPLE
a(3) = 4 because binomial(2*4,4) = 70 with 3 distinct prime divisors {2, 5, 7}.
MAPLE
with(numtheory): for n from 1 to 100 do:ii:=0: for k from 1 to 500 while(ii=0) do:x:=binomial(2*k, k):y:=factorset(x): n1:=nops(y):if n1=n then ii:=1:printf(`%d, `, k):else fi:od:if ii=0 then printf(`%d, `, 0):else fi:od:
CROSSREFS
KEYWORD
nonn
AUTHOR
Michel Lagneau, Jun 16 2012
STATUS
approved