0,2

Table of n, a(n) for n=0..77.

a(n)=Sum_digits[n*(n+1)], with n>=0

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);

Table[Total[IntegerDigits[n(n+1)]], {n, 0, 80}] (* Harvey P. Dale, May 14 2011 *)

Sequence in context: A136758 A056113 A251755 * A144531 A086357 A138054

Adjacent sequences: A128200 A128201 A128202 * A128204 A128205 A128206

easy,nonn,base

Paolo P. Lava and Giorgio Balzarotti, May 03 2007

approved