The OEIS mourns the passing of Jim Simons and is grateful to the Simons Foundation for its support of research in many branches of science, including the OEIS.
login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A129488 Smallest odd prime dividing binomial(2n,n). 4
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; text; internal format)
OFFSET
2,1
COMMENTS
The Erdős 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.
LINKS
P. Erdős, R. L. Graham, I. Z. Russa and E. G. Straus, On the prime factors of C(2n,n), Math. Comp. 29 (1975), 83-92.
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), A129489, A266366.
Sequence in context: A110551 A141334 A199614 * A211023 A279494 A053670
KEYWORD
nonn
AUTHOR
T. D. Noe, Apr 17 2007
STATUS
approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified May 26 16:43 EDT 2024. Contains 372840 sequences. (Running on oeis4.)