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A072503
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Number of ways to lace a shoe with n eyelet pairs such that there is no direct "horizontal" connection between any adjacent eyelet pair.
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0
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OFFSET
| 3,1
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COMMENTS
| The lacing must not have any "straight connections" between adjacent eyelet pairs (e.g. 2<->2*n-1, 3<->2*n-2, 4<->2*n-3,....). There are no symmetric solutions.
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LINKS
| Hugo Pfoertner, FORTRAN program to count non-straight shoe lacings and results for N=3,4
Index entries for sequences related to shoe lacings
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EXAMPLE
| The 6 non-straight lacings for n=3 are: 124536, 135426, 142356, 145326, 153246, 154236. Not counting mirror images we get a(3)=3.
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PROG
| FORTRAN program available at link.
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CROSSREFS
| Cf. A078602, A078698, A078702, A002866.
Sequence in context: A079484 A012494 A012780 * A154242 A163002 A117253
Adjacent sequences: A072500 A072501 A072502 * A072504 A072505 A072506
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KEYWORD
| nonn
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AUTHOR
| Hugo Pfoertner (hugo(AT)pfoertner.org), Jan 27 2003
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