id:A145389 - OEIS Search Results

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Digital roots of triangular numbers.

+0
6

0, 1, 3, 6, 1, 6, 3, 1, 9, 9, 1, 3, 6, 1, 6, 3, 1, 9, 9, 1, 3, 6, 1, 6, 3, 1, 9, 9, 1, 3, 6, 1, 6, 3, 1, 9, 9, 1, 3, 6, 1, 6, 3, 1, 9, 9, 1, 3, 6, 1, 6, 3, 1, 9, 9, 1, 3, 6, 1, 6, 3, 1, 9, 9, 1, 3, 6, 1, 6, 3, 1, 9, 9, 1, 3, 6, 1, 6, 3, 1, 9, 9, 1, 3, 6, 1, 6, 3, 1, 9, 9, 1, 3, 6, 1, 6, 3, 1, 9, 9, 1, 3, 6, 1, 6 (list; graph; listen)

	OFFSET	`0,3`
	COMMENT	`a(n) = A010888(A000217(n)).` `Periodic sequence for n>0: a(n+9) = a(n);` `a(A016777(n)) = 1; a(A007494(n)) <> 1;` `a(A090570(n)) = A010888(A090570(n)).`
	FORMULA	`a(n)=1+[(n^2+n-2)/2] mod 9. - Ant King, Apr 25 2009` `a(n)=(1/108){13(n mod 9)-83[(n+1) mod 9]+37[(n+2) mod 9]+49[(n+3) mod 9]-47[(n+4) mod 9]+73[(n+5) mod 9]-23[(n+6) mod 9]-11[(n+7) mod 9]+109[(n+8) mod 9]}-9[C(2n,n) mod 2], with n>=0 [From Paolo P. Lava (ppl(AT)spl.at), Oct 14 2008]`
	CROSSREFS	`Cf. A000217, A004157, A010888.` `Sequence in context: A078768 A089078 A134804 this_sequence A055263 A004157 A091068` `Adjacent sequences: A145386 A145387 A145388 this_sequence A145390 A145391 A145392`
	KEYWORD	`nonn`
	AUTHOR	`Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Oct 10 2008`

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Last modified November 24 23:16 EST 2009. Contains 167481 sequences.

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