OFFSET
1,2
COMMENTS
If n > 10, then 9 divides a(n). - Michel Lagneau, Dec 22 2011
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
EXAMPLE
5!! = 5*3*1 = 15 --> 1+5 = 6
MAPLE
P:=proc(n) local i, j, k, t1, t2; for i from 1 by 1 to n do j:=i; k:=i-2; while k>0 do j:=j*k; k:=k-2; od; t1:=j; t2:=0; while t1 <> 0 do t2:= t2+(t1 mod 10); t1 := floor(t1/10); od; print(t2); od; end: P(100);
MATHEMATICA
Table[Total[IntegerDigits[n!!]], {n, 70}] (* Harvey P. Dale, May 19 2021 *)
CROSSREFS
KEYWORD
easy,nonn,base
AUTHOR
Paolo P. Lava and Giorgio Balzarotti, Jun 30 2006
STATUS
approved