A109642 a(n) = least composite m such that binomial(3m,m) mod m = 3^n.

4, 15, 57, 765, 1025, 2097, 4947, 9189, 103599, 216927, 4346128, 1558269, 1977777

Offset

1,1

Comments

Subsequence of A109641.

Links

Table of n, a(n) for n=1..13.

Mathematica

In[1]:= n = 1; Do[If[ !PrimeQ[k] && Mod[Binomial[3*k, k], k] == 3^n, Print[k]; n++ ], {k, 1, 10^4}]

Crossrefs

Cf. A080469, A109641.

Sequence in context: A371777 A095930 A026850 * A307570 A164589 A017950

Adjacent sequences: A109639 A109640 A109641 * A109643 A109644 A109645

Keyword

nonn

Author

Ryan Propper, Aug 05 2005

Extensions

Edited by Max Alekseyev, Nov 03 2009

Status

approved