A208218 a(n)=(a(n-1)^2*a(n-3)+a(n-2))/a(n-4) with a(0)=a(1)=a(2)=a(3)=1.

1, 1, 1, 1, 2, 5, 27, 1463, 5350936, 154615586811211, 1295349936263652139582251464117, 6137049788665571444030885529267632764941063995324839557922175605

Offset: 0

Author

Matthew C. Russell, Apr 24 2012

Keywords

• nonn

Comments

This is the case a=1, b=1, c=2, y(0)=y(1)=y(2)=y(3)=1 of the recurrence shown in the Example 3.3 of "The Laurent phenomenon" (see Link lines, p. 10).

Links

• Seiichi Manyama, Table of n, a(n) for n = 0..14
• Sergey Fomin and Andrei Zelevinsky, The Laurent phenomenon, arXiv:math/0104241v1 [math.CO] (2001), Advances in Applied Mathematics 28 (2002), 119-144.

Crossrefs

Cf. A048736.

Programs

Magma

[n le 4 select 1 else (Self(n-1)^2*Self(n-3)+Self(n-2))/Self(n-4): n in [1..12]]; // Bruno Berselli, Apr 24 2012

Maple

y:=proc(n) if n<4 then return 1: fi: return (y(n-1)^2*y(n-3)+y(n-2))/y(n-4): end:
seq(y(n),n=0..11);

Mathematica

RecurrenceTable[{a[0]==a[1]==a[2]==a[3]==1,a[n]==(a[n-1]^2*a[n-3]+ a[n-2])/ a[n-4]},a,{n,12}] (* Harvey P. Dale, Dec 25 2016 *)