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Numbers having exactly one representation as sum of squares of primes.
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%I #4 Nov 07 2017 03:29:51

%S 4,8,9,12,13,16,17,18,20,21,22,24,26,27,28,30,31,32,35,39

%N Numbers having exactly one representation as sum of squares of primes.

%H <a href="/index/Su#ssq">Index entries for sequences related to sums of squares</a>

%F A090677(a(n)) = 1.

%t Flatten[Position[Rest[CoefficientList[Series[Product[1/(1 - x^(Prime[k]^2)), {k, 1, 5}], {x, 0, 40}], x]], 1]]

%Y Cf. A001248, A078135, A078136, A090677, A134755.

%K nonn,fini,full

%O 1,1

%A _Ilya Gutkovskiy_, Nov 02 2017