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A045865
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Theta series of quadratic form with Gram matrix [ 4, 0, 2, 1; 0, 2, 1, 1; 2, 1, 20, 1; 1, 1, 1, 10 ].
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1
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1, 2, 2, 4, 2, 4, 8, 4, 10, 6, 12, 12, 16, 4, 16, 16, 26, 20, 26, 16, 28, 20, 24, 24, 40, 14, 28, 20, 40, 12, 48, 16, 42, 36, 36, 32, 66, 2, 40, 32, 60, 16, 64, 40, 48, 52, 48, 36, 88, 30, 62, 56, 76, 32, 80, 48, 80, 56, 60, 56, 112, 52, 64, 72, 74, 56, 96, 40, 68, 72, 96, 28
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OFFSET
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0,2
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COMMENTS
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This is the 4-dimensional Elkies_A lattice.
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REFERENCES
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N. D. Elkies, Elliptic and modular curves..., in AMS/IP Studies in Advanced Math., 7 (1998), 21-76, esp. p. 57.
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LINKS
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EXAMPLE
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G.f. = 1 + 2*x + 2*x^2 + 4*x^3 + 2*x^4 + 4*x^5 + 8*x^6 + 4*x^7 + 10*x^8 + ...
G.f. = 1 + 2*q^2 + 2*q^4 + 4*q^6 + 2*q^8 + 4*q^10 + 8*q^12 + 4*q^14 + 10*q^16 + 6*q^18 + ...
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PROG
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(PARI) {a(n) = my(G); if( n<0, 0, G = [ 4, 0, 2, 1; 0, 2, 1, 1; 2, 1, 20, 1; 1, 1, 1, 10 ]; polcoeff( 1 + 2 * x * Ser( qfrep( G, n, 1)), n))}; /* Michael Somos, Mar 30 2015 */
(Magma) A := Basis( ModularForms( Gamma0(37), 2), 72); A[1] + 2*A[2] + 2*A[3]; /* Michael Somos, Mar 30 2015 */
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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EXTENSIONS
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More terms from Kok Seng Chua (chuaks(AT)ihpc.nus.edu.sg), Jun 22 2000
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STATUS
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approved
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