A011873 - OEIS

This site is supported by donations to The OEIS Foundation.

A011873

[ n(n-1)/20 ].

0, 0, 0, 0, 0, 1, 1, 2, 2, 3, 4, 5, 6, 7, 9, 10, 12, 13, 15, 17, 19, 21, 23, 25, 27, 30, 32, 35, 37, 40, 43, 46, 49, 52, 56, 59, 63, 66, 70, 74, 78, 82, 86, 90, 94, 99, 103, 108, 112, 117, 122, 127, 132, 137, 143, 148 (list; graph; refs; listen; history; internal format)

	OFFSET	`0,8`
	FORMULA	`a(n) = +2a(n-1) -a(n-2) +a(n-5) -2a(n-6) +a(n-7) -a(n-10) +2a(n-11) -a(n-12) +a(n-15) -2a(n-16) +a(n-17). G.f.: x^5(x^2-x+1)(x^6-x^3+1) / ((1-x)^3(x^2+1)(x^4+x^3+x^2+x+1)*(x^8-x^6+x^4-x^2+1) ). [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Apr 15 2010]`
	CROSSREFS	`Sequence in context: A001313 A057537 A065459 * A173151 A008673 A133564` `Adjacent sequences: A011870 A011871 A011872 * A011874 A011875 A011876`
	KEYWORD	`nonn`
	AUTHOR	`N. J. A. Sloane (njas(AT)research.att.com).`

Content is available under The OEIS End-User License Agreement .

Last modified February 14 23:53 EST 2012. Contains 205689 sequences.