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 A135618 #5 Nov 21 2013 12:49:09
%S A135618 1,2,1094,2899,56817,155286,3268191,9099642,12834909238,36503886401,
%T A135618 57494353262135,165465534734914,278352404864419302,807141068080455861,
%U A135618 19766110689810556002,57478249717507080819,1418604378354657012789
%N A135618 Even Motzkin numbers divided by 2.
%D A135618 E. Deutsch and B. E. Sagan, Congruences for Catalan and Motzkin numbers and related sequences, J. Num. Theory 117 (2006), 191-215.
%F A135618 a(n)=A134718(n)/2.
%t A135618 #/2&/@Select[Rest[RecurrenceTable[{a[0]==a[1]==1,a[n]==(3(n-1)a[n-2]+ (2n+1)a[n-1])/(n+2)},a,{n,60}]],EvenQ] (* _Harvey P. Dale_, Feb 27 2012 *)
%Y A135618 Cf. A001006, A134718.
%K A135618 nonn
%O A135618 1,2
%A A135618 _Omar E. Pol_, Feb 17 2008