A079069 a(n) = a(n-2) * a(n-3) + a(n-3), n>3. a(1) = a(2) = a(3) = 1.

1, 1, 1, 2, 2, 3, 6, 8, 21, 54, 176, 1155, 9558, 203456, 11040645, 1944642006, 2246285672576, 21470102051374515, 4368221476369196469462, 48227982626747161978326473216, 93786160880652497618461924784373935445

Offset

1,4

Links

Table of n, a(n) for n=1..21.

Maple

a:=proc(n) option remember; if n=1 then 1 elif n=2 then 1 elif n=3 then 1 else a(n-2)*a(n-3)+a(n-3); fi; end: seq(a(n), n=1..25); # Wesley Ivan Hurt, Jan 27 2017

Mathematica

RecurrenceTable[{a[1]==a[2]==a[3]==1, a[n]==a[n-2]a[n-3]+a[n-3]}, a, {n, 25}] (* Harvey P. Dale, Jul 18 2015 *)

Prog

(PARI) {a(n) = if( n<4, n>0, (1 + a(n-2)) * a(n-3))}

Crossrefs

Cf. A078919.

Sequence in context: A039870 A100948 A035571 * A019465 A077074 A163493

Adjacent sequences: A079066 A079067 A079068 * A079070 A079071 A079072

Keyword

nonn,easy

Author

Michael Somos, Dec 22 2002

Status

approved