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1, 2, 6, 33, 281, 3111, 41343, 635202, 11036914, 213638812, 4555901812, 106107724162, 2679887230354, 72962091956750, 2130453028323070, 66421485491085025, 2202438789394598209, 77400308039913410963
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OFFSET
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1,2
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COMMENTS
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Partial sums of number of irreducible diagrams (in the sense of perturbation expansion in quantum field theory: spinor case in 4 spacetime dimensions) with 2n nodes. The subsequence of primes in this partial sum begins: 2, 281, and there never seem to be any more, as the underlying sequence is all even after A000699(8).
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LINKS
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FORMULA
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EXAMPLE
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a(18) = 1 + 1 + 4 + 27 + 248 + 2830 + 38232 + 593859 + 10401712 + 202601898 + 4342263000 + 101551822350 + 2573779506192 + 70282204726396 + 2057490936366320 + 64291032462761955 + 2136017303903513184 + 75197869250518812754.
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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STATUS
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approved
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