1, 0, 1, 0, -2, 1, 0, 6, -6, 1, 0, -24, 36, -12, 1, 0, 120, -240, 120, -20, 1, 0, -720, 1800, -1200, 300, -30, 1, 0, 5040, -15120, 12600, -4200, 630, -42, 1, 0, -40320, 141120, -141120, 58800, -11760, 1176, -56, 1, 0, 362880, -1451520, 1693440, -846720, 211680, -28224, 2016, -72, 1
Offset: 0
Binomial convolution of row polynomials: p(3,x) = 6*x-6*x^2+x^3; p(2,x) = -2*x+x^2, p(1,x) = x, p(0,x) = 1,
together with those from A111595: s(3,x) = 9*x-6*x^2+x^3; s(2,x) = 1-2*x+x^2, s(1,x) = x, s(0,x) = 1; therefore
9*(x+y)-6*(x+y)^2+(x+y)^3 = s(3,x+y) = 1*s(0,x)*p(3,y) + 3*s(1,x)*p(2,y) + 3*s(2,x)*p(1,y) +1*s(3,x)*p(0,y) = (6*y-6*y^2+y^3) + 3*x*(-2*y+y^2) + 3*(1-2*x+x^2)*y + 9*x-6*x^2+x^3.
From _Wolfdieter Lang_, Apr 28 2014: (Start)
The triangle a(n,m) begins:
n\m 0 1 2 3 4 5 6 7
0: 1
1: 0 1
2: 0 -2 1
3: 0 6 -6 1
4: 0 -24 36 -12 1
5: 0 120 -240 120 -20 1
6: 0 -720 1800 -1200 300 -30 1
7: 0 5040 -15120 12600 -4200 630 -42 1
...
For more rows see the link.
(End)
A129256
Central coefficient of Product_{k=0..n} (1+k*x)^2.
Original entry on oeis.org
1, 2, 13, 144, 2273, 46710, 1184153, 35733376, 1251320145, 49893169050, 2232012515445, 110722046632560, 6032418472347265, 358103844593876654, 23007314730623658225, 1590611390957425536000, 117745011140615270168865
Offset: 0
This sequence equals the central terms of the triangle in which the g.f. of row n is (1+x)^2*(1+2x)^2*(1+3x)^2*...*(1+n*x)^2, as illustrated by:
(1);
1, (2), 1;
1, 6, (13), 12, 4;
1, 12, 58, (144), 193, 132, 36;
1, 20, 170, 800, (2273), 3980, 4180, 2400, 576;
1, 30, 395, 3000, 14523, (46710), 100805, 143700, 129076, 65760, 14400;
...
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Flatten[{1,Table[Coefficient[Expand[Product[(1+k*x),{k,0,n}]^2],x^n],{n,1,20}]}] (* Vaclav Kotesovec, Feb 10 2015 *)
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a(n)=polcoeff(prod(k=0,n,1+k*x)^2,n)
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{a(n)=(-1)^n*sum(k=0,n,stirling(n+1,k+1,1)*stirling(n+1,n-k+1,1))} \\ Paul D. Hanna, Jul 16 2009
A254881
Triangle read by rows, T(n,k) = sum(j=0..k-1, S(n+1,j+1)*S(n,k-j)) where S denotes the Stirling cycle numbers A132393, T(0,0)=1, n>=0, 0<=k<=2n.
Original entry on oeis.org
1, 0, 1, 1, 0, 2, 5, 4, 1, 0, 12, 40, 51, 31, 9, 1, 0, 144, 564, 904, 769, 376, 106, 16, 1, 0, 2880, 12576, 23300, 24080, 15345, 6273, 1650, 270, 25, 1, 0, 86400, 408960, 840216, 991276, 748530, 381065, 133848, 32523, 5370, 575, 36, 1, 0, 3628800, 18299520
Offset: 0
[1]
[0, 1, 1]
[0, 2, 5, 4, 1]
[0, 12, 40, 51, 31, 9, 1]
[0, 144, 564, 904, 769, 376, 106, 16, 1]
[0, 2880, 12576, 23300, 24080, 15345, 6273, 1650, 270, 25, 1]
For example in the case n=3 the polynomial (k^6+9*k^5+31*k^4+51*k^3+40*k^2+12*k)/3! generates the Lah numbers 0, 24, 240, 1200, 4200, 11760, 28224, ... (A253285).
The sequences
A000012,
A002378,
A083374,
A253285 are the Lah number rows generated by the polynomials divided by n! for n=0, 1, 2, 3 respectivly.
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# This is a special case of the recurrence given in A246117.
t := proc(n,k) option remember; if n=0 and k=0 then 1 elif
k <= 0 or k>n then 0 else iquo(n,2)*t(n-1,k)+t(n-1,k-1) fi end:
A254881 := (n,k) -> t(2*n,k):
seq(print(seq(A254881(n,k), k=0..2*n)), n=0..5);
# Illustrating the comment:
restart: with(PolynomialTools): with(CurveFitting): for N from 0 to 5 do
CoefficientList(PolynomialInterpolation([seq([k,N!*((N+k)!/k!)*binomial(N+k-1,k-1)], k=0..2*N)], n), n) od;
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Flatten[{1,Table[Table[Sum[Abs[StirlingS1[n+1,j+1]] * Abs[StirlingS1[n,k-j]],{j,0,k-1}],{k,0,2*n}],{n,1,10}]}] (* Vaclav Kotesovec, Feb 10 2015 *)
-
def T(n,k):
if n == 0: return 1
return sum(stirling_number1(n+1,j+1)*stirling_number1(n,k-j) for j in range(k))
for n in range (6): [T(n,k) for k in (0..2*n)]
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