OFFSET
0,5
COMMENTS
Also the number of prime divisors of A002944(n) = lcm_{j=0..floor(n/2)} binomial(n,j).
The terms are increasing by intervals, then decrease once. The local maxima are obtained for 23, 44, 47, 55, 62, 79, 83, 89, 104, 119, 131, 134, 139, 143, .... - Michel Marcus, Mar 21 2013
LINKS
T. D. Noe, Table of n, a(n) for n = 0..1000
FORMULA
MATHEMATICA
Table[prd = Product[Binomial[n, k], {k, 0, n}]; If[prd == 1, 0, Length[FactorInteger[prd]]], {n, 0, 100}] (* T. D. Noe, Mar 21 2013 *)
PROG
(PARI) a(n) = {sfp = Set(); for (k=1, n-1, sfp = setunion(sfp, Set(factor(binomial(n, k))[, 1]))); return (length(sfp)); } \\ Michel Marcus, Mar 21 2013
(Haskell)
a004788 = a001221 . a001142 -- Reinhard Zumkeller, Mar 16 2015
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved