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A084604 Triangle, read by rows, where the n-th row lists the (2n+1) coefficients of (1 + x + 4x^2)^n.

%I A084604 #16 Mar 03 2017 02:46:05
%S A084604 1,1,1,4,1,2,9,8,16,1,3,15,25,60,48,64,1,4,22,52,145,208,352,256,256,
%T A084604 1,5,30,90,285,561,1140,1440,1920,1280,1024,1,6,39,140,495,1206,2841,
%U A084604 4824,7920,8960,9984,6144,4096,1,7,49,203,791,2261,6027,12489,24108,36176
%N A084604 Triangle, read by rows, where the n-th row lists the (2n+1) coefficients of (1 + x + 4x^2)^n.
%H A084604 G. C. Greubel, <a href="/A084604/b084604.txt">Table of n, a(n) for the first 50 rows, flattened</a>
%e A084604 Rows:
%e A084604 {1},
%e A084604 {1,1, 4},
%e A084604 {1,2, 9,  8, 16},
%e A084604 {1,3,15, 25, 60,  48,  64},
%e A084604 {1,4,22, 52,145, 208, 352, 256, 256},
%e A084604 {1,5,30, 90,285, 561,1140,1440,1920,1280,1024},
%e A084604 {1,6,39,140,495,1206,2841,4824,7920,8960,9984,6144,4096},
%t A084604 With[{eq=(1+x+4x^2)},Flatten[Table[CoefficientList[Expand[eq^n],x],{n,0,10}]]] (* _Harvey P. Dale_, May 19 2011 *)
%o A084604 (PARI) for(n=0,10, for(k=0,2*n,t=polcoeff((1+x+4*x^2)^n,k,x); print1(t",")); print(" "))
%Y A084604 Cf. A002426, A084600-A084603, A084605-A084615.
%K A084604 nonn,tabf
%O A084604 0,4
%A A084604 _Paul D. Hanna_, Jun 01 2003