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A081580
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Pascal-(1,5,1) array.
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12
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1, 1, 1, 1, 7, 1, 1, 13, 13, 1, 1, 19, 61, 19, 1, 1, 25, 145, 145, 25, 1, 1, 31, 265, 595, 265, 31, 1, 1, 37, 421, 1585, 1585, 421, 37, 1, 1, 43, 613, 3331, 6145, 3331, 613, 43, 1, 1, 49, 841, 6049, 17401, 17401, 6049, 841, 49, 1, 1, 55, 1105, 9955, 40105, 65527, 40105, 9955, 1105, 55, 1
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OFFSET
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0,5
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COMMENTS
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One of a family of Pascal-like arrays. A007318 is equivalent to the (1,0,1)-array. A008288 is equivalent to the (1,1,1)-array. Rows include A016921, A081589, A081590. Coefficients of the row polynomials in the Newton basis are given by A013613.
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LINKS
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FORMULA
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Square array T(n, k) defined by T(n, 0) = T(0, k) = 1, T(n, k) = T(n, k-1) + 5*T(n-1, k-1) + T(n-1, k).
Rows are the expansions of (1+5*x)^k/(1-x)^(k+1).
Number triangle T(n,k) = Sum_{j=0..n-k} binomial(n-k,j)*binomial(k,j)*5^j.
Riordan array (1/(1-x), x*(1+5*x)/(1-x)). (End)
E.g.f. for the n-th subdiagonal, n = 0,1,2,..., equals exp(x)*P(n,x), where P(n,x) is the polynomial Sum_{k = 0..n} binomial(n,k)*(6*x)^k/k!. For example, the e.g.f. for the second subdiagonal is exp(x)*(1 + 12*x + 36*x^2/2) = 1 + 13*x + 61*x^2/2! + 145*x^3/3! + 265*x^4/4! + 421*x^5/5! + .... - Peter Bala, Mar 05 2017
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EXAMPLE
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Square array begins as:
1, 19, 145, 595, 1585, ... A081590;
1, 25, 265, 1585, 6145, ...
The triangle begins as:
1;
1, 1;
1, 7, 1;
1, 13, 13, 1;
1, 19, 61, 19, 1;
1, 25, 145, 145, 25, 1;
1, 31, 265, 595, 265, 31, 1;
1, 37, 421, 1585, 1585, 421, 37, 1;
1, 43, 613, 3331, 6145, 3331, 613, 43, 1;
1, 49, 841, 6049, 17401, 17401, 6049, 841, 49, 1;
1, 55, 1105, 9955, 40105, 65527, 40105, 9955, 1105, 55, 1; - Philippe Deléham, Mar 15 2014
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MATHEMATICA
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Table[Hypergeometric2F1[-k, k-n, 1, 6], {n, 0, 10}, {k, 0, n}]//Flatten (* Jean-François Alcover, May 24 2013 *)
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PROG
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(Magma)
A081580:= func< n, k, q | (&+[Binomial(k, j)*Binomial(n-j, k)*q^j: j in [0..n-k]]) >;
(Sage) flatten([[hypergeometric([-k, k-n], [1], 6).simplify() for k in (0..n)] for n in (0..12)]) # G. C. Greubel, May 26 2021
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CROSSREFS
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Cf. Pascal (1,m,1) array: A123562 (m = -3), A098593 (m = -2), A000012 (m = -1), A007318 (m = 0), A008288 (m = 1), A081577 (m = 2), A081578 (m = 3), A081579 (m = 4), A081581 (m = 6), A081582 (m = 7), A143683 (m = 8).
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KEYWORD
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AUTHOR
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STATUS
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approved
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