id:A025244 - OEIS Search Results

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a(n) = a(1)*a(n-1) + a(2)*a(n-2) + ...+ a(n-3)*a(3) for n >= 4.

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1, 1, 2, 2, 4, 10, 22, 52, 130, 326, 832, 2162, 5674, 15032, 40178, 108154, 292956, 797994, 2184430, 6006028, 16579138, 45929838, 127656504, 355863330, 994735442, 2787537904, 7829586914, 22038759218, 62158281844, 175636481738, 497142172806, 1409444977380 (list; graph; listen)

	OFFSET	`1,3`
	FORMULA	`G.f.: (1+x+x^2-sqrt(1-2x-x^2-6x^3+x^4))/2 - Michael Somos, Jun 08, 2000.`
	PROGRAM	`(PARI) a(n)=polcoeff((x+x^2-sqrt(1-2x-x^2-6x^3+x^4+x*O(x^n)))/2, n)`
	CROSSREFS	`Sequence in context: A002082 A005304 A100088 this_sequence A132824 A078801 A002420` `Adjacent sequences: A025241 A025242 A025243 this_sequence A025245 A025246 A025247`
	KEYWORD	`nonn`
	AUTHOR	`Clark Kimberling (ck6(AT)evansville.edu)`

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Last modified August 28 22:44 EDT 2008. Contains 143251 sequences.

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