id:A025226 - OEIS Search Results

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a(n) = a(1)*a(n-1) + a(2)*a(n-2) + ...+ a(n-1)*a(1) for n >= 2. Also a(n) = 3^n*C(n-1), where C = A000108 (Catalan numbers). E.g. a(3)=3^3*C(2)=27*2=54.

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3, 9, 54, 405, 3402, 30618, 288684, 2814669, 28146690, 287096238, 2975361012, 31241290626, 331638315876, 3553267670100, 38375290837080, 417331287853245, 4566095267100210 (list; graph; listen)

	OFFSET	`1,1`
	FORMULA	`G.f.: (1-sqrt(1-12x))/2 - Michael Somos, Jun 08, 2000.` `Given g.f. C(x) and given A(x)= g.f. of A100239, then B(x)=A(x)-1-2x satisfies B(x)=x-C(xB(x)). - Michael Somos Sep 07 2005`
	PROGRAM	`(PARI) a(n)=polcoeff((1-sqrt(1-12x+xO(x^n)))/2, n)`
	CROSSREFS	`Cf. A000108, A005159.` `Sequence in context: A013341 A077795 A038496 this_sequence A001194 A032179 A075979` `Adjacent sequences: A025223 A025224 A025225 this_sequence A025227 A025228 A025229`
	KEYWORD	`nonn`
	AUTHOR	`Clark Kimberling (ck6(AT)evansville.edu)`

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Last modified September 7 15:23 EDT 2008. Contains 143483 sequences.

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