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Search: id:A059116
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| A059116 |
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The sequence lambda(4,n), where lambda is defined in A055203. Number of ways of placing n identifiable positive intervals with a total of exactly four starting and/or finishing points. |
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+0
4
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| 0, 0, 6, 114, 978, 6810, 43746, 271194, 1653378, 9998970, 60229986, 362088474, 2174656578, 13054316730, 78345032226, 470127588954, 2820937720578
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OFFSET
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0,3
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COMMENT
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For all n, a(n)=1*6^n-4*3^n+6*1^n-4*0^n+1*0^n [with 0^0=1] where powers are taken of triangular numbers and multiplied by binomial coefficients with alternating signs.
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FORMULA
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For n>0, a(n) =6^n-4*3^n+6.
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EXAMPLE
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a(2)=6 since intervals a-a and b-b can be combined as a-a-b-b, a-b-a-b, a-b-b-a, b-a-b-a, b-a-a-b, or b-a-a-b.
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CROSSREFS
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Cf. A058809, A059117.
Sequence in context: A088668 A066931 A051228 this_sequence A121544 A003425 A052465
Adjacent sequences: A059113 A059114 A059115 this_sequence A059117 A059118 A059119
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KEYWORD
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nonn
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AUTHOR
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Henry Bottomley (se16(AT)btinternet.com), Jan 05 2001
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