A141522 a(1) = 0, a(2) = a(3) = 1; a(n) = a(n-1)*a(n-2) + a(n-1)*a(n-3) for n > 3.

0, 1, 1, 1, 2, 4, 12, 72, 1152, 96768, 118444032, 11598039613440, 1374840894208868352000, 15945621994910596019667697926144000, 21922693387137438627357958684974264478793362424463360000

Offset

1,5

References

Martin Gardner, Mathematical Circus, Random House, New York, 1981, p. 165.

Links

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

Mathematica

Nest[Append[#, #[[-1]] #[[-2]] + #[[-1]] #[[-3]]] &, {0, 1, 1}, 12] (* Michael De Vlieger, Dec 17 2017 *)

Prog

(MATLAB)
function y=fib(n)
%Generates running geometric numbers( second kind)
fz(1)=0; fz(2)=1; fz(3)=1;
for k=4:n
fz(k)=fz(k-1)*(fz(k-2)+fz(k-3));
end
y=fz(n);
(PARI) /* script that avoids arrays */
geom(n) = {
local(a=0, b=1, c=1, d);
print1(a", "b", "c", ");
for(x=1, n-3,
d=(a+b)*c;
print1(d", ");
a=b; b=c; c=d;
)
} \\ Cino Hilliard, Apr 29 2009

Crossrefs

Sequence in context: A078919 A085864 A060935 * A114903 A038054 A003180

Adjacent sequences: A141519 A141520 A141521 * A141523 A141524 A141525

Keyword

nonn

Author

Matt Wynne (matwyn(AT)verizon.net), Aug 11 2008

Status

approved