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 A291846 #11 Sep 03 2017 16:58:23
%S A291846 1,1,5,33,283,2995,37723,551047,9157923,170606547,3521075919,
%T A291846 79741123539,1965955092517,52414187219485,1502559229282213,
%U A291846 46087421890091145,1506033038595292467,52232959640093489043,1916263566511685329711,74142047814365044902307,3017192203838382727894241,128829022389463544587355721,5758871157244067281788041809
%N A291846 Central terms in irregular triangle A291845.
%C A291846 G.f. of row n in triangle A291845 equals Product_{k=0..n-1} (1 + (2*k+1)*x + x^2), with row sums equal to the odd double factorials A001147.
%H A291846 Paul D. Hanna, <a href="/A291846/b291846.txt">Table of n, a(n) for n = 0..300</a>
%F A291846 a(n) = A291845(n,n).
%o A291846 (PARI) /* As Central Terms of Triangle A291845 */
%o A291846 {A291845(n, k)=polcoeff(prod(j=0, n-1, 1 + (2*j+1)*x + x^2), k)}
%o A291846 {for(n=0,25,print1(A291845(n,n),", "))}
%Y A291846 Cf. A291845, A291847, A291848.
%K A291846 nonn
%O A291846 0,3
%A A291846 _Paul D. Hanna_, Sep 03 2017