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A005415 Tensors with n external gluons.
(Formerly M2080)
1
1, 0, 1, 2, 15, 140, 1915, 33810, 734545, 18929960, 564216345, 19088149850, 722508543295, 30249199720740, 1387823333771875, 69238799231051450, 3731906171773805025, 216101966957781304400, 13379538319131196637425, 881962125004262056604850 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

COMMENTS

See Fig. 26, p. 1549 in the Cvitanovic reference. - Jonathan Vos Post, Feb 20 2010

REFERENCES

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

LINKS

Alois P. Heinz, Table of n, a(n) for n = 0..368

P. Cvitanovic, Group theory for Feynman diagrams in non-Abelian gauge theories, Phys. Rev. D14 (1976), 1536-1553.

FORMULA

a(n) = Sum_{k=0..n-1} binomial(n-1, k) * a(k) * b(n-k) where b(1) = 0, b(2) = 1, b(n) = 2^(n-2) * (2*n-5)!! = A001813(n-2) [From Cvitanovic]. - Sean A. Irvine, Jun 17 2016

CROSSREFS

Cf. A001813.

Sequence in context: A215922 A285449 A288950 * A219868 A224885 A253571

Adjacent sequences:  A005412 A005413 A005414 * A005416 A005417 A005418

KEYWORD

nonn,nice

AUTHOR

N. J. A. Sloane

EXTENSIONS

More terms from Sean A. Irvine, Jun 17 2016

STATUS

approved

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Last modified February 19 16:28 EST 2018. Contains 299356 sequences. (Running on oeis4.)