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A031358
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Number of coincidence site lattices of index 4n+1 in lattice Z^2.
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0
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1, 2, 0, 2, 2, 0, 2, 2, 0, 2, 2, 0, 0, 2, 0, 2, 4, 0, 2, 0, 0, 4, 2, 0, 2, 2, 0, 2, 2, 0, 0, 2, 0, 0, 2, 0, 4, 2, 0, 2, 0, 0, 2, 2, 0, 2, 4, 0, 2, 2, 0, 4, 0, 0, 0, 4, 0, 2, 2, 0, 2, 0, 0, 0, 2, 0, 4, 2, 0, 2, 2, 0, 2, 2, 0, 0, 4, 0, 2, 2, 0, 4, 0, 0, 2, 0, 0, 2, 2, 0, 0, 4, 0, 2, 4, 0, 0, 2, 0, 2, 2, 0, 2, 0, 0, 2
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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REFERENCES
| M. Baake, "Solution of coincidence problem...", in R. V. Moody, ed., Math. of Long-Range Aperiodic Order, Kluwer 1997, pp. 9-44.
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FORMULA
| Dirichlet series: Product (1+p^(-s))/(1-p^(-s)); p == 1 (mod 4).
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PROG
| (PARI) t1=direuler(p=2, 1200, (1+(p%4<2)*X))
t2=direuler(p=2, 1200, 1/(1-(p%4<2)*X))
t3=dirmul(t1, t2)
t4=vector(200, n, t3[4*n+1]) (and then prepend 1)
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CROSSREFS
| Cf. A175647.
Sequence in context: A123530 A161516 A123063 * A029317 A127800 A035692
Adjacent sequences: A031355 A031356 A031357 * A031359 A031360 A031361
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KEYWORD
| nonn,easy,nice
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
| More terms from N. J. A. Sloane (njas(AT)research.att.com), Mar 13 2009
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