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%I #30 Dec 09 2020 01:31:15
%S 0,0,0,0,0,0,0,0,1,0,0,0,0,2,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,2,0,0,0,0,
%T 2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,2,0,0,0,0,2,0,0,0,0,0,0,0,0,0,
%U 0,0,0,0,0,0,2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1
%N Expansion of (Sum_{k>=1} x^(prime(k)^2))^2.
%C Number of ordered ways of writing n as the sum of two squares of primes (A001248).
%H <a href="/index/Su#ssq">Index entries for sequences related to sums of squares</a>
%F G.f.: (Sum_{k>=1} x^(prime(k)^2))^2.
%F a(n) = Sum_{i=1..n} A302048(i)*A302048(n-i). - _Ridouane Oudra_, Nov 21 2020
%e a(13) = 2 because we have [4, 9] and [9, 4].
%t nmax = 125; CoefficientList[Series[(Sum[x^Prime[k]^2, {k, 1, nmax}])^2, {x, 0, nmax}], x]
%Y Cf. A001248, A063725, A073610, A302048.
%K nonn
%O 0,14
%A _Ilya Gutkovskiy_, Dec 24 2016
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