A000644 - OEIS

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A000644

Loops of length 4n on square grid that turn at each step and return to start in original direction.

1, 1, 3, 7, 31, 138, 808, 4956, 33047, 227328 (list; graph; refs; listen; history; internal format)

	OFFSET	`0,3`
	REFERENCES	`D. E. Knuth, The Texbook, p. 390.` `D. E. Knuth, personal communication.`
	CROSSREFS	`Sequence in context: A123488 A121620 A042271 * A015459 A115083 A141385` `Adjacent sequences: A000641 A000642 A000643 * A000645 A000646 A000647`
	KEYWORD	`nonn,nice`
	AUTHOR	`N. J. A. Sloane (njas(AT)research.att.com).`

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Last modified February 14 07:16 EST 2012. Contains 205589 sequences.