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A168422 Number triangle with row sums given by quadruple factorial numbers A001813. 2

%I #16 Mar 31 2023 14:41:04

%S 1,1,1,7,4,1,71,39,9,1,1001,536,126,16,1,18089,9545,2270,310,25,1,

%T 398959,208524,49995,7120,645,36,1,10391023,5394991,1301139,190435,

%U 18445,1197,49,1,312129649,161260336,39066076,5828704,589750,41776,2044,64,1

%N Number triangle with row sums given by quadruple factorial numbers A001813.

%C Reversal of coefficient array for the polynomials P(n,x) = Sum_{k=0..n} (C(n+k,2k)*(2k)!/k!)*x^k*(1-x)^(n-k).

%C Note that P(n,x) = Sum_{k=0..n} A113025(n,k)*x^k*(1-x)^(n-k). Row sums are A001813.

%H William P. Orrick, <a href="/A168422/b168422.txt">Table of n, a(n) for n = 0..10010</a>

%F T(n,k) = (1/k!)*Sum_{j=k..n} (-1)^(j-k)*(2*n-j)!/((n-j)!*(j-k)!).

%e Triangle begins

%e 1

%e 1 1

%e 7 4 1

%e 71 39 9 1

%e 1001 536 126 16 1

%e 18089 9545 2270 310 25 1

%e 398959 208524 49995 7120 645 36 1

%e 10391023 5394991 1301139 190435 18445 1197 49 1

%e 312129649 161260336 39066076 5828704 589750 41776 2044 64 1

%e Production matrix begins

%e 1 1

%e 6 3 1

%e 40 20 5 1

%e 336 168 42 7 1

%e 3456 1728 432 72 9 1

%e 42240 21120 5280 880 110 11 1

%e 599040 299520 74880 12480 1560 156 13 1

%e 9676800 4838400 1209600 201600 25200 2520 210 15 1

%e Complete this with a top row (1,0,0,0,...) and invert: we get

%e 1

%e -1 1

%e -3 -3 1

%e -5 -5 -5 1

%e -7 -7 -7 -7 1

%e -9 -9 -9 -9 -9 1

%e -11 -11 -11 -11 -11 -11 1

%e -13 -13 -13 -13 -13 -13 -13 1

%e -15 -15 -15 -15 -15 -15 -15 -15 1

%e -17 -17 -17 -17 -17 -17 -17 -17 -17 1

%o (SageMath)

%o def T(n,k):

%o return(sum((-1)^(j-k) * binomial(2*n-j,n) * binomial(n,j)\

%o * binomial(j,k) * factorial(n-j)\

%o for j in range(k,n+1))) # _William P. Orrick_, Mar 24 2023

%o (PARI) T(n,k)={sum(j=k, n, (-1)^(j-k)*(2*n-j)!/((n-j)!*(j-k)!))/k!} \\ _Andrew Howroyd_, Mar 24 2023

%Y Column 1 is |A002119|.

%Y Sum_{k=0..n} T(n,k) * 2^k, is A001517(n).

%Y Cf. A079267.

%K easy,nonn,tabl

%O 0,4

%A _Paul Barry_, Nov 25 2009

%E Corrected and extended by _William P. Orrick_, Mar 24 2023

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Last modified March 28 08:22 EDT 2024. Contains 371236 sequences. (Running on oeis4.)