This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A123486 #16 Oct 14 2017 20:54:23
%S A123486 1,2,1,4,2,1,8,8,2,1,16,16,12,2,1,32,48,24,16,2,1,64,96,96,32,20,2,1,
%T A123486 128,256,192,160,40,24,2,1,256,512,640,320,240,48,28,2,1,512,1280,
%U A123486 1280,1280,480,336,56,32,2,1,1024,2560,3840,2560,2240,672,448,64,36,2,1
%N A123486 Riordan array (1/(1-2*x), x/(1-4*x^2)).
%C A123486 Row sums are A026581. Diagonal sums are A026383.
%H A123486 G. C. Greubel, <a href="/A123486/b123486.txt">Table of n, a(n) for the first 50 rows, flattened</a>
%F A123486 Number triangle T(n,k) = C(floor((n+k)/2), k) * 2^(n-k).
%F A123486 T(n,k) = T(n-1,k-1) + 4*T(n-2,k), T(0,0) = 1, T(1,0) = 2, T(1,1) = 1, T(n,k) = 0 if k<0 or if k>n. - _Philippe Deléham_, Jan 20 2014
%e A123486 Number triangle begins
%e A123486 1;
%e A123486 2, 1;
%e A123486 4, 2, 1;
%e A123486 8, 8, 2, 1;
%e A123486 16, 16, 12, 2, 1;
%e A123486 32, 48, 24, 16, 2, 1;
%t A123486 Table[Binomial[Floor[(n + k)/2], k]*2^(n - k), {n, 0, 49}, {k, 0,
%t A123486 n}] // Flatten (* _G. C. Greubel_, Oct 13 2017 *)
%o A123486 (PARI) for(n=0,10, for(k=0,n, print1(binomial(floor((n+k)/2),k)*2^(n-k), ", "))) \\ _G. C. Greubel_, Oct 13 2017
%K A123486 easy,nonn,tabl
%O A123486 0,2
%A A123486 _Paul Barry_, Sep 30 2006
%E A123486 Terms a(46) onward added by _G. C. Greubel_, Oct 14 2017