A084678 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).

1, 2, 3, 6, 5, 190, 7, 2415, 84, 31626, 11, 10485409451852020512869123005636410508621081799664615969238750, 13, 5887596, 4509005501, 652786136966869378239977875665, 17

Offset

1,2

Comments

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

a(18) > 10^150.

Links

Table of n, a(n) for n=1..17.

Example

Set of divisors of n=10: {1,2,5,10}, binomial(10,5)=252 ->
binomial(252,2)=31626 -> binomial(31626,1)=31626=a(10).

Crossrefs

Sequence in context: A228151 A276087 A341837 * A221020 A333304 A248896

Adjacent sequences: A084675 A084676 A084677 * A084679 A084680 A084681

Keyword

nonn

Author

Reinhard Zumkeller, Jun 28 2003

Status

approved