%I A109769
%S A109769 18,25,133,2107,4676,226037,4477739,827867201
%N A109769 Composite n such that binomial(7*n, n) == 7^n (mod n).
%C A109769 No other terms below 10^9.
%H A109769 Max Alekseyev, <a href="http://cse.sc.edu/~maxal/gpscripts/">PARI/GP 
               scripts for various problems</a>
%e A109769 18 is a term because binomial(7*18, 18) = 2797093093529137508875, 7^18 
               = 1628413597910449 and 2797093093529137508875 mod 18 = 1628413597910449 
               mod 18 = 1.
%t A109769 Do[If[ !PrimeQ[n], If[Mod[Binomial[7*n, n], n] == Mod[7^n, n], Print[n]]], 
               {n, 2, 20000}]
%Y A109769 Cf. A080469.
%Y A109769 Sequence in context: A072422 A003300 A084379 this_sequence A093018 A167336 
               A003634
%Y A109769 Adjacent sequences: A109766 A109767 A109768 this_sequence A109770 A109771 
               A109772
%K A109769 more,nonn,new
%O A109769 1,1
%A A109769 Ryan Propper (rpropper(AT)stanford.edu), Aug 13 2005
%E A109769 226037 from Max Alekseyev (maxale(AT)gmail.com), Sep 13 2009
%E A109769 Two more terms from Max Alekseyev (maxale(AT)gmail.com), Nov 06 2009