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 A281423 #6 Jan 22 2017 21:53:15
%S A281423 0,0,0,1,2,1,0,2,2,0,2,3,0,0,2,0,0,3,2,0,0,2,2,2,2,0,2,0,0,2,0,3,2,0,
%T A281423 0,4,4,0,2,2,0,1,2,2,2,2,0,2,0,2,4,0,0,0,2,0,2,4,0,1,2,0,2,4,0,2,2,1,
%U A281423 0,2,2,2,2,0,0,4,0,0,0,2,2,2,0,1,6,0,0,2,2,0,0,2,2,2,2,2,2,4,4,2,0,2,0,0,2,4,0,2,4,1,2,4
%N A281423 Expansion of (Sum_{k>=1} x^prime(prime(k)))^2 [even terms only].
%C A281423 Number of ways to write 2n as an ordered sum of two primes with prime subscripts (A006450).
%H A281423 Ilya Gutkovskiy, <a href="/A281423/a281423.pdf">Extended graphical example</a>
%H A281423 <a href="/index/Com#comp">Index entries for sequences related to compositions</a>
%F A281423 G.f.: (Sum_{k>=1} x^prime(prime(k)))^2 [even terms only].
%e A281423 a(4) = 2 because we have [3, 5] and [5, 3], where 3 = prime(2) = prime(prime(1)) and 5 = prime(3) = prime(prime(2)).
%t A281423 Take[CoefficientList[Series[Sum[x^Prime[Prime[k]], {k, 1, 250}]^2, {x, 0, 250}], x], {1, -1, 2}]
%Y A281423 Cf. A001031, A002375, A006450, A045917, A073610, A281422.
%K A281423 nonn
%O A281423 0,5
%A A281423 _Ilya Gutkovskiy_, Jan 21 2017