A123702 a(1)=a(2)=1. For n >= 3, a(n) = (product{k=1 to n-1} a(k)) - (sum{j=1 to n-1} a(j)).

1, 1, -1, -2, 3, 4, 18, 408, 175824, 30989858688, 960376803619751958528, 922323604960653729254933704147036248735744, 850680832267616036448642743307003648114050501920269009809993262836200003241653567488

Offset

1,4

Comments

a(3) and a(4) are the only negative terms of the sequence.

Links

Table of n, a(n) for n=1..13.

Formula

For n >= 5, a(n) = a(n-1) a(n-2) (a(n-1)-1) /(a(n-2)-1).

Mathematica

f[l_List] := Append[l, Times @@ l - Plus @@ l]; Nest[f, {1, 1}, 11] (* Ray Chandler, Oct 09 2006 *)

Crossrefs

Cf. A123703.

Sequence in context: A077407 A273002 A333547 * A265367 A265902 A245453

Adjacent sequences: A123699 A123700 A123701 * A123703 A123704 A123705

Keyword

easy,sign

Author

Leroy Quet, Oct 08 2006

Extensions

Extended by Ray Chandler, Oct 09 2006

Status

approved