id:A128203 - OEIS Search Results

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Sum of the digits of n*(n+1).

+0
1

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; listen)

	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);`
	CROSSREFS	`Sequence in context: A011042 A136758 A056113 this_sequence A144531 A086357 A138054` `Adjacent sequences: A128200 A128201 A128202 this_sequence A128204 A128205 A128206`
	KEYWORD	`easy,nonn,base`
	AUTHOR	`Paolo P. Lava & Giorgio Balzarotti (ppl(AT)spl.at), May 03 2007`

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Last modified November 25 20:09 EST 2009. Contains 167514 sequences.

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