A101921 - OEIS

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A101921

a(2n) = a(n) + 2n - 1, a(2n+1) = 4n.

0, 1, 4, 4, 8, 9, 12, 11, 16, 17, 20, 20, 24, 25, 28, 26, 32, 33, 36, 36, 40, 41, 44, 43, 48, 49, 52, 52, 56, 57, 60, 57, 64, 65, 68, 68, 72, 73, 76, 75, 80, 81, 84, 84, 88, 89, 92, 90, 96, 97, 100, 100, 104, 105, 108, 107, 112, 113, 116, 116, 120, 121, 124, 120, 128 (list; graph; refs; listen; history; internal format)

	OFFSET	`1,3`
	COMMENTS	`Exponent of 2 in tangent numbers A000182. Also, exponent of 2 in the sequences A008775, A009670, A009764, A009798, A012227, A024236, A024277, A024299, A052510.`
	FORMULA	`a(n) = 2[A000265(n)-1] - A007814(n) + 2n[1-(1/2)^A007814(n)].` `G.f.: Sum[k>=0, t^2(t^2+4t+1)/(1-t^2)^2, t=x^2^k].`
	CROSSREFS	`Equals A007814(A000182(n)).` `Sequence in context: A168273 A145447 A204989 * A093340 A046558 A180854` `Adjacent sequences: A101918 A101919 A101920 * A101922 A101923 A101924`
	KEYWORD	`nonn`
	AUTHOR	`Ralf Stephan (ralf(AT)ark.in-berlin.de), Dec 21 2004`

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Last modified February 16 13:12 EST 2012. Contains 205909 sequences.