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 A337053 #5 Aug 13 2020 08:58:45
%S A337053 1,1,0,1,1,4,81,81,2500,71289,170569,4752400,314388361,2553584089,
%T A337053 12138750976,3868290439209,98777141491561,74627448683524,
%U A337053 77548359598953721,6456459980629467081,96370747288471888164,738333256838429983201,526354651474052521626801
%N A337053 a(n) = exp(2) * Sum_{i>=0} Sum_{j>=0} (-1)^(i+j) * (i*j)^n / (i! * j!).
%C A337053 Squares of complementary Bell numbers.
%F A337053 a(n) = A000587(n)^2.
%t A337053 Table[Exp[2] Sum[Sum[(-1)^(i + j) (i j)^n/(i! j!), {j, 0, Infinity}], {i, 0, Infinity}], {n, 0, 22}]
%t A337053 Table[BellB[n, -1]^2, {n, 0, 22}]
%Y A337053 Cf. A000587, A001247, A121869.
%K A337053 nonn
%O A337053 0,6
%A A337053 _Ilya Gutkovskiy_, Aug 12 2020