OFFSET
0,3
LINKS
Harvey P. Dale, Table of n, a(n) for n = 0..1000
Eric Weisstein's World of Mathematics, Multifactorial.
FORMULA
a(n) = 1 for n<1, else a(n) = n*a(n-8).
Sum_{n>=0} 1/a(n) = A288095. - Amiram Eldar, Nov 10 2020
EXAMPLE
a(10) = 10 * a(10-8) = 10 * a(2) = 10 * 2 = 20.
a(20) = 20 * a(20-8) = 20 * a(12) = 20 * (12*a(12-8)) = 20 * 12 * a(4) = 20 * 12 * 4 = 960.
a(30) = 30 * a(30-8) = 30 * a(22) = 30 * (22*a(22-8)) = 30 * 22 * a(14) = 30 * 22 * (14*a(14-8)) = 30 * 22 * 14 * 6 = 55440.
MAPLE
A114800 := proc(n)
option remember;
if n < 1 then
1;
else
n*procname(n-8) ;
end if;
end proc:
seq(A114800(n), n=0..40) ; # R. J. Mathar, Jun 23 2014
MATHEMATICA
Table[Times@@Range[n, 1, -8], {n, 0, 50}] (* Harvey P. Dale, Feb 17 2018 *)
PROG
(PARI) a(n)=if(n<1, 1, n*a(n-8));
vector(50, n, n--; a(n) ) \\ G. C. Greubel, Aug 21 2019
(Magma) b:=func< n | n le 8 select n else n*Self(n-8) >;
[1] cat [b(n): n in [1..50]]; // G. C. Greubel, Aug 21 2019
(Sage)
def a(n):
if (n<1): return 1
else: return n*a(n-8)
[a(n) for n in (0..50)] # G. C. Greubel, Aug 21 2019
(GAP)
a:= function(n)
if n<1 then return 1;
else return n*a(n-8);
fi;
end;
List([0..50], n-> a(n) ); # G. C. Greubel, Aug 21 2019
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Jonathan Vos Post, Feb 18 2006
STATUS
approved