A160143 - OEIS

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A160143

A 'look-a-like' of the coefficients of the series for x/cos(x).

1, 3, 25, 427, 12465, 555731, 35135945, 2990414715, 329655706465, 45692713833379, 1111113564712575, 1595024111042171723, 387863354088927172625, 110350957750914345093747 (list; graph; refs; listen; history; internal format)

	OFFSET	`0,2`
	COMMENTS	`The first difference with sequence A009843 (expansion of x/cos(x)) occurs at a(10). An explanation can be found in the 'look-a-like' of the numerators of (2n+1)/(4^(2n+1)-2^(2*n+1)) with the odd numbers 2n+1 (cf. A160144).` `A156769 describes a similar 'look-a-like' with A036279 (expansion of tan(x)).`
	MAPLE	`a := n -> (-1)^iquo(n, 2)euler(n)(n+1)/(4^(n+1)-2^(n+1));` `seq(numer(a(2*n)), n=0..13);`
	CROSSREFS	`Cf. A009843, A160144, A160145, A036279, A156769.` `Sequence in context: A192552 A143925 A074708 * A009843 A182962 A136173` `Adjacent sequences: A160140 A160141 A160142 * A160144 A160145 A160146`
	KEYWORD	`frac,nonn`
	AUTHOR	`Peter Luschny (peter(AT)luschny.de), May 03 2009`

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Last modified February 16 17:48 EST 2012. Contains 205939 sequences.