A084678 - OEIS

%I #3 Mar 30 2012 18:50:35

%S 1,2,3,6,5,190,7,2415,84,31626,11,

%T 10485409451852020512869123005636410508621081799664615969238750,13,

%U 5887596,4509005501,652786136966869378239977875665,17

%N a(n)=b(n,n) with b(n,1)=n and b(n,k)=binomial(b(n,k-1),d(n,n-k+1)) for 1<k<=n, where d(n,i) are the divisors of n, d(i)<d(j), 1<=i<j<=A000005(n).

%C n>1: a(n) = n iff n is prime;

%C a(18) > 10^150.

%e Set of divisors of n=10: {1,2,5,10}, binomial(10,5)=252 ->

%e binomial(252,2)=31626 -> binomial(31626,1)=31626=a(10).

%K nonn

%O 1,2

%A _Reinhard Zumkeller_, Jun 28 2003