A111289 a(1) = a(2) = a(3) = a(4) = 1. For n>= 5, a(n) = a(n-1)*a(n-4) + a(n-2)*a(n-3).

1, 1, 1, 1, 2, 3, 5, 11, 37, 166, 1237, 19749, 936055, 179814643, 240916863586, 4926183534613279, 4654499108310829164143, 838133896191338105830469104443, 201943518452400520392903690464302135967495, 994814736615560793049792416556718062880283217474796953454

Offset

1,5

Links

Table of n, a(n) for n=1..20.

Mathematica

nxt[{a_, b_, c_, d_}]:={b, c, d, a*d+b*c}; NestList[nxt, {1, 1, 1, 1}, 20][[;; , 1]] (* Harvey P. Dale, Feb 23 2023 *)

Prog

(PARI) a(n)=if(n<5, 1, a(n-1)*a(n-4) + a(n-2)*a(n-3)) (Klasen)

Crossrefs

Sequence in context: A167604 A065510 A006721 * A255420 A127181 A323611

Adjacent sequences: A111286 A111287 A111288 * A111290 A111291 A111292

Keyword

easy,nonn

Author

Leroy Quet, Nov 01 2005

Extensions

More terms from Lambert Klasen (lambert.klasen(AT)gmx.net), Nov 06 2005

Status

approved