A068928 - OEIS

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A068928

Number of incongruent ways to tile a 3 X 2n room with 1x2 Tatami mats. At most 3 Tatami mats may meet at a point.

2, 2, 2, 4, 5, 9, 12, 21, 30, 51, 76, 127, 195, 322, 504, 826, 1309, 2135, 3410, 5545, 8900, 14445, 23256, 37701, 60813, 98514, 159094, 257608, 416325, 673933, 1089648, 1763581, 2852242, 4615823, 7466468, 12082291, 19546175, 31628466 (list; graph; refs; listen; history; internal format)

	OFFSET	`1,1`
	FORMULA	`For n >= 8, a(n) = a(n-1) + 2*a(n-2) - a(n-3) - a(n-5) - a(n-6).` `O.g.f.: x(2-4x^2-x^4+x^6)/((1-x-x^2)(1-x^2-x^4)). a(n) = (A000045(n+1)+A053602(n+1))/2, n>1. [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Aug 30 2008]`
	CROSSREFS	`Cf. A068922 for total number of tilings, A068926 for more info.` `Essentially the same as A001224.` `Sequence in context: A057591 A024405 A082547 * A152968 A086420 A170887` `Adjacent sequences: A068925 A068926 A068927 * A068929 A068930 A068931`
	KEYWORD	`easy,nonn`
	AUTHOR	`Dean Hickerson (dean.hickerson(AT)yahoo.com), Mar 11 2002`

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Last modified February 16 19:41 EST 2012. Contains 205947 sequences.