|
| |
|
|
A129488
|
|
Smallest odd prime dividing binomial(2n,n).
|
|
3
| |
|
|
3, 5, 5, 3, 3, 3, 3, 5, 11, 3, 7, 5, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 7, 5, 3, 7, 7, 3, 3, 3, 3, 7, 7, 3, 5, 5, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 5, 5, 3, 5, 5, 3, 3, 3, 3, 5, 5, 3, 5, 5, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 2,1
|
|
|
COMMENTS
| The Erdos paper calls this function g(n) and states that it not known whether it is bounded. Currently, g(3160)=13 is the greatest known value of g. See A129489.
|
|
|
REFERENCES
| P. Erdos, R. L. Graham, I. Z. Russa and E. G. Straus, On the prime factors of C(2n,n), Math. Comp. 29 (1975), 83-92.
|
|
|
LINKS
| T. D. Noe, Table of n, a(n) for n = 2..5000
|
|
|
MATHEMATICA
| Table[Transpose[FactorInteger[Binomial[2n, n]]][[1, 2]], {n, 2, 150}]
|
|
|
PROG
| (PARI) a(n)=my(k); forprime(p=3, default(primelimit), k=1; while((k*=p)<=2*n, if(n/k-n\k>1/2, return(p)))) \\ Charles R Greathouse IV, Dec 19 2011
|
|
|
CROSSREFS
| Cf. A030979 (n such that g(n)=11).
Sequence in context: A110551 A141334 A199614 * A053670 A085963 A184593
Adjacent sequences: A129485 A129486 A129487 * A129489 A129490 A129491
|
|
|
KEYWORD
| nonn
|
|
|
AUTHOR
| T. D. Noe (noe(AT)sspectra.com), Apr 17 2007
|
| |
|
|
