A263047 a(1)=0, a(2)=1, a(3)=2; for n>3, a(n) = a(n-3)*a(n-1) - a(n-2).

0, 1, 2, -1, -3, -5, 8, -19, 87, 715, -13672, -1190179, -850964313, 11634385277515, -13847001034356560872, 11783303722311508585098883421, 137091495347348713307137824784782074139687, -1898306077876225285447341619480271058010077969630158545410485

Offset: 1

Author

Gianmarco Giordano, Oct 08 2015

Keywords

• sign

Programs

Magma

[n le 3 select n-1 else Self(n-3)*Self(n-1)-Self(n-2): n in [1..20]]; // Vincenzo Librandi, Oct 09 2015

Maple

a[1]:= 0: a[2]:= 1: a[3]:= 2:
for n from 4 to 20 do
  a[n]:= a[n-3]*a[n-1]-a[n-2]
od:
seq(a[i],i=1..20); # Robert Israel, Oct 08 2015

Mathematica

nxt[{a_,b_,c_}]:={b,c,a*c-b}; NestList[nxt,{0,1,2},20][[All,1]] (* Harvey P. Dale, Feb 02 2022 *)

PARI

a(n) = if(n<4, n-1, a(n-3)*a(n-1)-a(n-2));
vector(20, n, a(n)) \\ Altug Alkan, Oct 08 2015