A086356 Fixed point if [nonzero-digit product]-function at initial-value=C[2n,n]=central binomial coefficient is iterated.

2, 6, 2, 7, 2, 4, 4, 2, 2, 6, 6, 6, 8, 6, 5, 8, 8, 4, 8, 2, 9, 8, 6, 8, 6, 2, 8, 8, 2, 8, 6, 2, 6, 6, 8, 2, 6, 6, 6, 8, 9, 2, 2, 8, 2, 8, 2, 8, 6, 4, 2, 2, 8, 8, 2, 8, 6, 8, 2, 8, 6, 8, 9, 6, 6, 2, 6, 2, 2, 2, 8, 6, 8, 6, 8, 2, 8, 8, 8, 8, 8, 8, 6, 2, 6, 2, 8, 6, 8, 8, 8, 8, 8, 6, 8, 8, 6, 8, 2, 8, 2, 8, 6, 8, 8

Offset: 1

Author

Labos Elemer, Jul 21 2003

Keywords

• base
• nonn

Examples

			n=10, C[20,10]=184756, iteration list={184756,7560,210,2},
a(100)=2.
		

Crossrefs

Cf. A051801, A051802, A086353-A086361, A029898, A010888, A038194, A000984.

Programs

Mathematica

prd[x_] := Apply[Times, DeleteCases[IntegerDigits[x], 0]] Table[FixedPoint[prd, Binomial[2*n, n]], {w, 1, 128}]

Formula

a(n)=A051802[A000984(n)]=fixed-point of A051801[C(2n, n)]