A002495 - OEIS

A002495

Theta series of 27-dimensional unimodular lattice with root system A_1 with no parity vector of norm 3.

1, 0, 2, 2676, 101118, 1644784, 16044996, 110148864, 584716268, 2549726784, 9515920164, 31314134428, 92917720104, 252775518960, 638328487880, 1511740834560, 3387163064214, 7228599229760, 14768913424614, 29023937463900, 55107648867544, 101434033397472

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OFFSET

0,3

REFERENCES

R. Bacher and B. B. Venkov, Réseaux entiers unimodulaires sans racine en dimension 27 et 28, in Réseaux euclidiens, designs sphériques et formes modulaires, pp. 212-267, Enseignement Math., Geneva, 2001.

LINKS

Table of n, a(n) for n=0..21.

R. Bacher and B. B. Venkov, Réseaux entiers unimodulaires sans racine en dimension 27 et 28

FORMULA

G.f.: theta3^27 - 54*theta3^19*delta8 + 218*theta3^11*delta8^2 where theta3 = A000122 and delta8 = A002408. - Sean A. Irvine, Feb 28 2020

CROSSREFS

Cf. A000122, A002408, A002434, A002490.

Sequence in context: A324426 A114067 A109119 * A353126 A242109 A078457

Adjacent sequences: A002492 A002493 A002494 * A002496 A002497 A002498

KEYWORD

nonn

AUTHOR

N. J. A. Sloane

EXTENSIONS

More terms from Sean A. Irvine, Feb 28 2020

STATUS

approved