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%I #11 Jun 01 2021 11:45:24
%S 43,113,331,1019,1559,1613,2087,2551,3217,5471,6317,7109,7583,7703,
%T 11777,13967,15649,18353,21277,22921,24847,27767,27997,29167,66617,
%U 86531,91081,91921,112289,116041,122267,122753,123727,125197,138289
%N Prime numbers p such that pi(p) + 2*p is a square.
%F a(n) = prime(A104776(n)).
%t Select[Prime[Range[13000]],IntegerQ[Sqrt[PrimePi[#]+2 #]]&] (* _Harvey P. Dale_, Jun 01 2021 *)
%o (PARI) lista(nn) = {vec = vector(nn, i, prime(i)); pp = select(i->(issquare(2*i+primepi(i))), vec); pp;} \\ _Michel Marcus_, Oct 09 2013
%Y Cf. A104776.
%K nonn
%O 1,1
%A _Zak Seidov_, Apr 23 2005
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