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 A005874 Theta series of hexagonal close-packing with respect to triangle between tetrahedra. (Formerly M2236) 1
 0, 3, 2, 0, 3, 12, 0, 6, 0, 6, 0, 12, 6, 6, 12, 12, 3, 0, 2, 6, 0, 24, 0, 24, 6, 3, 0, 24, 6, 12, 12, 6, 0, 12, 0, 0, 18, 6, 12, 48, 0, 24, 0, 6, 0, 36, 0, 0, 6, 9, 14, 24, 6, 12, 12, 0, 0, 48, 0, 36, 24, 6, 12 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 REFERENCES N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS S. K. K. Choi, A. V. Kumchev and R. Osburn, On sums of three squares, arXiv:math/0502007 [math.NT], 2005. N. J. A. Sloane and B. K. Teo, Theta series and magic numbers for close-packed spherical clusters, J. Chem. Phys. 83 (1985) 6520-6534. FORMULA Sum_{n<=x} a(n)^2 ~ (8*Pi^4/(21*zeta(3))) * x^2. (Choi/Kumchev/Osburn) CROSSREFS Sequence in context: A331922 A198826 A088161 * A275622 A129239 A224825 Adjacent sequences:  A005871 A005872 A005873 * A005875 A005876 A005877 KEYWORD nonn,easy,more AUTHOR EXTENSIONS Formula corrected by Vaclav Kotesovec, Oct 25 2015 STATUS approved

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Last modified February 24 01:03 EST 2020. Contains 332195 sequences. (Running on oeis4.)