A123919 - OEIS

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A123919

Number of numbers congruent to 2 or 4 mod 6 and <= n.

0, 1, 1, 2, 2, 2, 2, 3, 3, 4, 4, 4, 4, 5, 5, 6, 6, 6, 6, 7, 7, 8, 8, 8, 8, 9, 9, 10, 10, 10, 10, 11, 11, 12, 12, 12, 12, 13, 13, 14, 14, 14, 14, 15, 15, 16, 16, 16, 16, 17, 17, 18, 18, 18, 18, 19, 19, 20, 20, 20, 20, 21, 21, 22, 22, 22, 22, 23, 23, 24, 24, 24, 24, 25, 25, 26, 26, 26 (list; graph; refs; listen; history; text; internal format)

	OFFSET	`1,4`
	COMMENTS	`First differences of A056827. [From R. J. Mathar, Nov 22 2008]`
	LINKS	`Table of n, a(n) for n=1..78.`
	FORMULA	`G.f.: x^2(1+x^2)/((1+x)(1-x)^2*(1+x+x^2)(1-x+x^2)). a(n+1)-a(n)=A120325(n+1). [From R. J. Mathar, Nov 22 2008]`
	MATHEMATICA	`f[n_] := Floor[n/2] - Floor[n/6]; Array[f, 78] (* Robert G. Wilson v Oct 29 2006 *)`
	CROSSREFS	`Cf. A047235.` `Sequence in context: A189671 A109497 A156078 * A194324 A194328 A194304` `Adjacent sequences: A123916 A123917 A123918 * A123920 A123921 A123922`
	KEYWORD	`easy,nonn`
	AUTHOR	`Giovanni Teofilatto, Oct 29 2006`
	STATUS	`approved`

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Last modified June 20 09:31 EDT 2013. Contains 226422 sequences.