A011883 - OEIS

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A011883

[ n(n-1)/30 ].

0, 0, 0, 0, 0, 0, 1, 1, 1, 2, 3, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 15, 16, 18, 20, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 42, 44, 46, 49, 52, 54, 57, 60, 63, 66, 69, 72, 75, 78, 81, 85, 88, 91, 95, 99, 102, 106, 110, 114, 118, 122, 126, 130, 134, 138, 143, 147, 151, 156, 161, 165 (list; graph; refs; listen; history; internal format)

	OFFSET	`0,10`
	FORMULA	`a(n) = +2a(n-1) -a(n-2) +a(n-15) -2a(n-16) +a(n-17). G.f.: x^6(x^2-x+1)(x^4-x^2+1) / ( (1-x)^3(1+x^4+x^3+x^2+x)(1+x+x^2)*(1-x+x^3-x^4+x^5-x^7+x^8) ). [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Apr 15 2010]`
	CROSSREFS	`Sequence in context: A029928 A101788 A024698 * A034886 A011882 A025767` `Adjacent sequences: A011880 A011881 A011882 * A011884 A011885 A011886`
	KEYWORD	`nonn`
	AUTHOR	`N. J. A. Sloane (njas(AT)research.att.com).`
	EXTENSIONS	`More terms from Vladimir Orlovsky (4vladimir(AT)gmail.com), Mar 14 2010`

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Last modified February 15 20:03 EST 2012. Contains 205852 sequences.