OFFSET
0,2
FORMULA
a(n)=Sum_digits[n*(n+1)], with n>=0
MAPLE
P:=proc(n) local i, k, w; for i from 0 by 1 to n do w:=0; k:=i*(i+1); while k>0 do w:=w+k-(trunc(k/10)*10); k:=trunc(k/10); od; print(w); od; end: P(100);
MATHEMATICA
Table[Total[IntegerDigits[n(n+1)]], {n, 0, 80}] (* Harvey P. Dale, May 14 2011 *)
CROSSREFS
KEYWORD
easy,nonn,base
AUTHOR
Paolo P. Lava and Giorgio Balzarotti, May 03 2007
STATUS
approved