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Search: id:A000644
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A000644 Loops of length 4n on square grid that turn at each step and return to start in original direction. +0
1
1, 1, 3, 7, 31, 138, 808, 4956, 33047, 227328 (list; graph; listen)
OFFSET

0,3

REFERENCES

D. E. Knuth, The Texbook, p. 390.

D. E. Knuth, personal communication.

CROSSREFS

Sequence in context: A123488 A121620 A042271 this_sequence A015459 A115083 A141385

Adjacent sequences: A000641 A000642 A000643 this_sequence A000645 A000646 A000647

KEYWORD

nonn,nice

AUTHOR

N. J. A. Sloane (njas(AT)research.att.com).

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Last modified November 27 14:50 EST 2009. Contains 167570 sequences.


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