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A123876 Riordan array (1/(1+2*x), x*(1+x)/(1+2*x)^2). 4

%I

%S 1,-2,1,4,-5,1,-8,18,-8,1,16,-56,41,-11,1,-32,160,-170,73,-14,1,64,

%T -432,620,-377,114,-17,1,-128,1120,-2072,1666,-704,164,-20,1,256,

%U -2816,6496,-6608,3649,-1178,223,-23,1,-512,6912,-19392,24192,-16722,7001,-1826,291,-26,1

%N Riordan array (1/(1+2*x), x*(1+x)/(1+2*x)^2).

%C Inverse of A116395.

%C Row sums are A123877.

%C Diagonal sums are (-1)^n*A085810(n).

%C Unsigned version is A114164.

%H G. C. Greubel, <a href="/A123876/b123876.txt">Rows n = 0..100 of triangle, flattened</a>

%F Number triangle T(n,k) = (-1)^(n-k)*Sum_{j=0..n} C(k,j-k)*C(n,j)*2^(n-j).

%F T(n,k) = T(n-1,k-1) - 4*T(n-1,k) + T(n-2,k-1) - 4*T(n-2,k), T(0,0) = T(1,1) = 1, T(1,0) = -2, T(n,k) = 0 if k<0 or if k>n. - _Philippe Deléham_, Jan 18 2014

%e Triangle begins

%e 1;

%e -2, 1;

%e 4, -5, 1;

%e -8, 18, -8, 1;

%e 16, -56, 41, -11, 1;

%e -32, 160, -170, 73, -14, 1;

%t Table[(-1)^(n-k)*Sum[2^(n-j)*Binomial[k,j-k]*Binomial[n,j], {j,0,n}], {n,0,12}, {k,0,n}]//Flatten (* _G. C. Greubel_, Aug 08 2019 *)

%o (PARI) T(n,k) = b=binomial; (-1)^(n-k)*sum(j=0,n, 2^(n-j)*b(k,j-k)* b(n,j)); \\ _G. C. Greubel_, Aug 08 2019

%o (MAGMA) [(-1)^(n-k)*(&+[2^(n-j)*Binomial(k,j-k)*Binomial(n,j): j in [0..n]]): k in [0..n], n in [0..12]]; // _G. C. Greubel_, Aug 08 2019

%o (Sage)

%o b=binomial;

%o [[(-1)^(n-k)*sum(2^(n-j)*b(k,j-k)*b(n,j) for j in (0..n)) for k in (0..n)] for n in (0..12)] # _G. C. Greubel_, Aug 08 2019

%o (GAP) Flat(List([0..12], n-> List([0..n], k-> (-1)^(n-k)*Sum([0..n], j-> 2^(n-j)*Binomial(k,j-k)*Binomial(n,j) ))));

%Y Cf. A085810, A114164, A116395, A123877.

%K easy,sign,tabl

%O 0,2

%A _Paul Barry_, Oct 16 2006

%E More terms added by _G. C. Greubel_, Aug 08 2019

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Last modified September 20 20:12 EDT 2019. Contains 327247 sequences. (Running on oeis4.)