A125594 a(1)=1, a(2)=2, a(3)=4, a(n)=C(C(a(n-1),a(n-2)),C(a(n-1),a(n-2))).

1, 2, 4, 15, 8885554239441880

Offset

1,2

Comments

Next term has 306322 digits. For a(1)=1, a(2)=2 and a(3)=1,2,3, sequence ends with 1's: 1, 2, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1,... 1, 2, 2, 0, 0, 1, 1, 1, 1, 1, 1, 1,... 1, 2, 3, 3, 0, 0, 1, 1, 1, 1, 1, 1,...

Links

Table of n, a(n) for n=1..5.

Mathematica

a=1; b=2; c=4; s={a, b, c}; Do[d=Binomial[Binomial[c, b], Binomial[b, a]]; AppendTo[s, d]; a=b; b=c; c=d, {3}]; s IntegerDigits[s[[ -1]]]//Length 306322

Crossrefs

Sequence in context: A378300 A132483 A153064 * A097542 A277850 A332352

Adjacent sequences: A125591 A125592 A125593 * A125595 A125596 A125597

Keyword

nonn

Author

Zak Seidov, Jan 05 2007

Status

approved