This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A128203 Sum of the digits of n*(n+1). 0
 0, 2, 6, 3, 2, 3, 6, 11, 9, 9, 2, 6, 12, 11, 3, 6, 11, 9, 9, 11, 6, 12, 11, 12, 6, 11, 9, 18, 11, 15, 12, 20, 12, 6, 11, 9, 9, 11, 15, 12, 11, 12, 15, 20, 18, 9, 11, 15, 12, 11, 12, 15, 20, 18, 18, 11, 15, 12, 11, 12, 15, 20, 18, 9, 11, 15, 12, 20, 21, 15, 20, 9, 18, 11, 15, 12, 20, 12 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS 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 Sequence in context: A136758 A056113 A251755 * A144531 A086357 A138054 Adjacent sequences:  A128200 A128201 A128202 * A128204 A128205 A128206 KEYWORD easy,nonn,base AUTHOR Paolo P. Lava and Giorgio Balzarotti, May 03 2007 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified October 18 14:52 EDT 2019. Contains 328161 sequences. (Running on oeis4.)