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Search: id:A153836
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| A153836 |
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a(n) = 2^(n^2) - 2^(n^2-n+1) for n >= 1; a(0) = 0. |
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+0
1
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| 0, 0, 8, 384, 57344, 31457280, 66571993088, 554153860399104, 18302628885633695744, 2408406906263519058984960, 1265174720149658640946904956928, 2655859843140564331993348872396079104
(list; graph; listen)
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OFFSET
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0,3
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COMMENT
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Number of binary relations on an n-element set that are neither reflexive nor irreflexive. Note that "irreflexive" = "antireflexive".
The empty relation, unlike all others, is (trivially) both reflexive and irreflexive.
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FORMULA
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a(n) = 2^(n^2) - 2^(n^2-n+1) = A002416(n) - 2*A053763(n) for n >= 1; a(0) = 0.
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PROGRAM
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(PARI) a(n) = if(n<=0, 0, 2^(n^2)-2^(n^2-n+1))
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CROSSREFS
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Cf. A002416, A053763.
Sequence in context: A162445 A067624 A096204 this_sequence A151941 A085806 A042115
Adjacent sequences: A153833 A153834 A153835 this_sequence A153837 A153838 A153839
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KEYWORD
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nonn
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AUTHOR
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Rick L. Shepherd (rshepherd2(AT)hotmail.com), Jan 02 2009
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