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 A046647 #18 Mar 08 2020 00:23:02 %S A046647 1,6,26,120,594,3094,16728,93024,528770,3058770,17948970,106585440, %T A046647 639318456,3867821640,23574446992,144621823632,892293152994, %U A046647 5533289372170,34468829508750,215594574231960,1353464311979010 %N A046647 Number of certain rooted planar maps. %H A046647 W. G. Brown, <a href="http://dx.doi.org/10.4153/CJM-1963-056-7">Enumeration of non-separable planar maps</a>, Canad. J. Math., 15 (1963), 526-545. %H A046647 W. G. Brown, <a href="/A000087/a000087.pdf">Enumeration of non-separable planar maps</a> [Annotated scanned copy] %F A046647 a(2)=1; a(n) = 4*(7*n-15)*(3*n-6)!/((n-2)!*(2n-2)!). - _Emeric Deutsch_, Mar 03 2004 %F A046647 G.f.: (g+1)*(3*g+1)/(g-1)^2 where g*(1-g)^2 = x. - _Mark van Hoeij_, Nov 10 2011 %Y A046647 A diagonal of A046651. Cf. A046646. %K A046647 nonn,easy %O A046647 2,2 %A A046647 _N. J. A. Sloane_ %E A046647 More terms from _Emeric Deutsch_, Mar 03 2004