A006197 Least number not dividing binomial(2n,n). (Formerly M2297)

3, 4, 3, 3, 5, 5, 5, 4, 3, 3, 5, 3, 3, 7, 7, 4, 7, 8, 9, 8, 7, 7, 7, 7, 5, 5, 3, 3, 9, 3, 3, 4, 8, 8, 5, 3, 3, 9, 3, 3, 13, 13, 13, 11, 11, 11, 11, 8, 7, 5, 5, 5, 13, 9, 5, 5, 5, 7, 7, 5, 5, 5, 7, 4, 7, 7, 9, 8, 13, 7, 7

Offset

1,1

Comments

All terms are prime powers (A246655). [Corrected by Amiram Eldar, May 27 2024]

References

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

T. D. Noe, Table of n, a(n) for n=1..10000

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.

Formula

a(n) = A007978(A000984(n)). - Amiram Eldar, May 27 2024

Mathematica

a[n_] := Module[{k = 1, b = Binomial[2*n, n]}, While[Divisible[b, k], k++]; k]; Array[a, 100] (* Amiram Eldar, May 27 2024 *)

Crossrefs

Cf. A000984, A007978, A246655.

Sequence in context: A322347 A373712 A073322 * A079404 A349945 A246820

Adjacent sequences: A006194 A006195 A006196 * A006198 A006199 A006200

Keyword

nonn

Author

N. J. A. Sloane

Status

approved