id:A085584 - OEIS Search Results

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Number of (3412,2341)-, (3412,4123)-, and (3412,52341)-avoiding involutions in S_n.

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1, 2, 4, 9, 20, 45, 100, 222, 491, 1086, 2401, 5310, 11744, 25977, 57460, 127101, 281144, 621882, 1375579, 3042726, 6730385, 14887338, 32930188, 72840249, 161119700, 356390301, 788321020, 1743734406, 3857070395, 8531684622 (list; graph; listen)

	OFFSET	`1,2`
	LINKS	`E. S. Egge, Restricted 3412-Avoiding Involutions: Continued Fractions, Chebyshev Polynomials and Enumerations, sec. 8`
	FORMULA	`G.f. (1-x^2)(1-x)^2/(1-3x+x^2+3x^3-3x^4).`
	CROSSREFS	`Sequence in context: A090245 A091620 A108469 this_sequence A080019 A052534 A080135` `Adjacent sequences: A085581 A085582 A085583 this_sequence A085585 A085586 A085587`
	KEYWORD	`nonn,easy`
	AUTHOR	`Ralf Stephan (ralf(AT)ark.in-berlin.de), Jul 06 2003`

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Last modified August 19 23:53 EDT 2008. Contains 142930 sequences.

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