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 A027284 #12 Dec 15 2021 07:13:42
%S A027284 5,28,167,1024,6359,39759,249699,1573524,9943905,62994733,399936573,
%T A027284 2543992514,16210331727,103453402718,661164765879,4230874777682,
%U A027284 27105456280491,173838468040879,1115987495619427,7170725839251598,46113396476943241,296773029762031990
%N A027284 a(n) = Sum_{k=0..2*n-2} T(n,k) * T(n,k+2), with T given by A026584.
%H A027284 G. C. Greubel, <a href="/A027284/b027284.txt">Table of n, a(n) for n = 2..1000</a>
%F A027284 a(n) = Sum_{k=0..2*n-2} A026584(n,k) * A026584(n,k+2).
%t A027284 T[n_, k_]:= T[n, k]= If[k==0 || k==2*n, 1, If[k==1 || k==2*n-1, Floor[n/2], If[EvenQ[n+k], T[n-1, k-2] + T[n-1, k], T[n-1, k-2] + T[n-1, k-1] + T[n-1, k] ]]]; (* T = A026584 *)
%t A027284 a[n_]:= a[n]= Sum[T[n, k]*T[n, k+2], {k, 0, 2*n-2}];
%t A027284 Table[a[n], {n, 2, 40}] (* _G. C. Greubel_, Dec 15 2021 *)
%o A027284 (Sage)
%o A027284 @CachedFunction
%o A027284 def T(n, k): # T = A026584
%o A027284 if (k==0 or k==2*n): return 1
%o A027284 elif (k==1 or k==2*n-1): return (n//2)
%o A027284 else: return T(n-1, k-2) + T(n-1, k) if ((n+k)%2==0) else T(n-1, k-2) + T(n-1, k-1) + T(n-1, k)
%o A027284 @CachedFunction
%o A027284 def A027284(n): return sum(T(n,j)*T(n, j+2) for j in (0..2*n-2))
%o A027284 [A027284(n) for n in (2..40)] # _G. C. Greubel_, Dec 15 2021
%Y A027284 Cf. A026584, A026585, A026587, A026589, A026590, A026591, A026592, A026593, A026594, A026595, A026596, A026597, A026598, A026599, A027282, A027283, A027285, A027286.
%K A027284 nonn
%O A027284 2,1
%A A027284 _Clark Kimberling_
%E A027284 More terms from _Sean A. Irvine_, Oct 26 2019