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A062966
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a(n) = C(3+n, n) + C(4+n, n) + C(5+n, n) + C(6+n, n).
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2
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4, 22, 74, 195, 441, 896, 1680, 2958, 4950, 7942, 12298, 18473, 27027, 38640, 54128, 74460, 100776, 134406, 176890, 229999, 295757, 376464, 474720, 593450, 735930, 905814, 1107162, 1344469, 1622695, 1947296
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OFFSET
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0,1
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COMMENTS
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In the Frey-Sellers reference this sequence is called {(n+2) over 6}_{3}, n >= 0.
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LINKS
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FORMULA
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a(n) = A062750(n+2, 6) = (n+10)*(n+3)*(n+2)*(n+1)*(n^2+11*n+48)/6!.
G.f.: N(4;1, x)/(1-x)^7 with N(4;1, x) = 4-6*x+4*x^2-x^3, polynomial of second row of A062751.
a(0)=4, a(1)=22, a(2)=74, a(3)=195, a(4)=441, a(5)=896, a(6)=1680, a(n) = 7*a(n-1) - 21*a(n-2) + 35*a(n-3) - 35*a(n-4) + 21*a(n-5) - 7*a(n-6) + a(n-7). - Harvey P. Dale, May 02 2012
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MATHEMATICA
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Table[Sum[Binomial[i+n, n], {i, 3, 6}], {n, 0, 30}] (* or *) LinearRecurrence[ {7, -21, 35, -35, 21, -7, 1}, {4, 22, 74, 195, 441, 896, 1680}, 30] (* Harvey P. Dale, May 02 2012 *)
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PROG
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(PARI) { for (n=0, 1000, a=binomial(3 + n, n) + binomial(4 + n, n) + binomial(5 + n, n) + binomial(6 + n, n); write("b062966.txt", n, " ", a) ) } \\ Harry J. Smith, Aug 14 2009
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CROSSREFS
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Seventh column (r=6) of FS(4) staircase array A062750.
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KEYWORD
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nonn,easy
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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