|
|
A066459
|
|
Product of factorials of the digits of n.
|
|
7
|
|
|
1, 1, 2, 6, 24, 120, 720, 5040, 40320, 362880, 1, 1, 2, 6, 24, 120, 720, 5040, 40320, 362880, 2, 2, 4, 12, 48, 240, 1440, 10080, 80640, 725760, 6, 6, 12, 36, 144, 720, 4320, 30240, 241920, 2177280, 24, 24, 48, 144, 576, 2880, 17280, 120960, 967680
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
0,3
|
|
LINKS
|
Eric Weisstein's World of Mathematics, Factorial
|
|
FORMULA
|
If n=10*q+r, (0 <= r < 10) then a(n) = (q+1+r)!*Sum_{k=0..r} (-1)^(q-k)*binomial(r,k)/(q+1+r-k). - Milan Janjic, Dec 14 2008
|
|
EXAMPLE
|
a(24) = (2!) * (4!) = 2 * 24 = 48.
|
|
MAPLE
|
local a, d;
a := 1 ;
for d in convert(n, base, 10) do
a := a*d! ;
end do:
a ;
|
|
PROG
|
(PARI) { for (n=0, 1000, m=n; a=1; while (m>0, d=m%10; m=(m-d)/10; a*=d!); write("b066459.txt", n, " ", a) ) } \\ Harry J. Smith, Feb 15 2010
(Haskell)
import Data.List (unfoldr)
a066459 = product . map a000142 .
unfoldr (\x -> if x == 0 then Nothing else Just $ swap $ divMod x 10)
(Python)
import math
s=1
for i in str(n):
s*=math.factorial(int(i))
|
|
CROSSREFS
|
|
|
KEYWORD
|
base,easy,nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|