OFFSET
0,2
EXAMPLE
0!!=1
1!!=1 -> 1+1=2
2!!=2 -> 2+2=4
3!!=3 -> 4+3=7
4!!=8 -> 7+8=15 -> 1+5=6
5!!=15 -> 15+15=30 -> 3+0=3
MAPLE
P:=proc(n) local i, j, k, w, sf; sf:=1; for i from 0 by 1 to n do k:=i; w:=i-2; while w>0 do k:=k*w; w:=w-2; od; sf:=sf+k; w:=0; k:=sf; while k>0 do w:=w+k-(trunc(k/10)*10); k:=trunc(k/10); od; print(w); od; end: P(100);
CROSSREFS
KEYWORD
easy,nonn,base
AUTHOR
Paolo P. Lava and Giorgio Balzarotti, Jun 14 2007
STATUS
approved