A010690 - OEIS

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A010690

Period 2: repeat (1,9).

1, 9, 1, 9, 1, 9, 1, 9, 1, 9, 1, 9, 1, 9, 1, 9, 1, 9, 1, 9, 1, 9, 1, 9, 1, 9, 1, 9, 1, 9, 1, 9, 1, 9, 1, 9, 1, 9, 1, 9, 1, 9, 1, 9, 1, 9, 1, 9, 1, 9, 1, 9, 1, 9, 1, 9, 1, 9, 1, 9, 1, 9, 1, 9, 1, 9, 1, 9, 1, 9, 1, 9, 1, 9, 1, 9, 1, 9, 1, 9, 1 (list; graph; refs; listen; history; internal format)

	OFFSET	`0,2`
	COMMENTS	`Digital roots of the non-zero square triangular numbers. - Ant King, Jan 21 2012`
	LINKS	`Index to sequences with linear recurrences with constant coefficients, signature (0,1).`
	FORMULA	`a(n)=-4(-1)^n+5 =9(n mod 2)+(n+1) mod 2 - Paolo P. Lava (paoloplava(AT)gmail.com), Oct 20 2006` `G.f. (1+9x)/((1-x)(1+x)). - R. J. Mathar, Nov 21 2011`
	MATHEMATICA	`5+4(-1)^# &/@Range[81] ( Ant King, Jan 21 2012 *)`
	CROSSREFS	`Sequence in context: A175615 A200696 A203130 * A067617 A021525 A197724` `Adjacent sequences: A010687 A010688 A010689 * A010691 A010692 A010693`
	KEYWORD	`nonn,easy`
	AUTHOR	`N. J. A. Sloane (njas(AT)research.att.com).`

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Last modified February 16 06:18 EST 2012. Contains 205860 sequences.