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A008655
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Theta series of direct sum of 4 copies of hexagonal lattice.
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1
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1, 24, 216, 888, 1752, 3024, 7992, 8256, 14040, 24216, 27216, 31968, 64824, 52752, 74304, 111888, 112344, 117936, 217944, 164640, 220752, 305472, 287712, 292032, 519480, 378024, 474768, 654072
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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COMMENTS
| The hexagonal lattice is the familiar 2-dimensional lattice in which each point has 6 neighbors. This is sometimes called the triangular lattice.
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REFERENCES
| J. H. Conway and N. J. A. Sloane, "Sphere Packings, Lattices and Groups", Springer-Verlag, p. 110.
J. McKay and A. Sebbar, Fuchsian groups, automorphic functions and Schwarzians, Math. Ann., 318 (2000), 255-275.
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LINKS
| G. Nebe and N. J. A. Sloane, Home page for hexagonal (or triangular) lattice A2
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FORMULA
| Expansion of (theta_3(z)*theta_3(3z)+theta_2(z)*theta_2(3z))^4.
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CROSSREFS
| Sequence in context: A105946 A050222 A169635 * A133754 A104670 A205968
Adjacent sequences: A008652 A008653 A008654 * A008656 A008657 A008658
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KEYWORD
| nonn,easy
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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