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%I #7 Nov 18 2021 02:37:23
%S 0,0,1,3,4,8,8,13,15,16,16,20,22,30,32,33,33,41,44,50,54,58,58,66,69,
%T 73,76,76,78,88,88,100,103,107,109,111,113,123,127,129,131,142,146,
%U 159,165,167,169,183,191,193,197,201,204,214,218,224,230,233,233,245,252,268
%N Number of prime pairs (p,q) with p^2 + q^2 <= n^2.
%H Jean-François Alcover, <a href="/A097689/b097689.txt">Table of n, a(n) for n = 1..10000</a>
%t a[n_] := a[n] = Module[{cnt = 0, p, q}, Do[p = Prime[ip]; q = Prime[iq]; If[p^2 + q^2 <= n^2, If[p == q, cnt++, If[p < q, cnt += 2, 0]]], {ip, PrimePi[n]}, {iq, ip, PrimePi[n]}]; cnt];
%t Array[a, 100] (* _Jean-François Alcover_, Nov 18 2021 *)
%Y Cf. A001182, A000720.
%K nonn
%O 1,4
%A _Reinhard Zumkeller_, Sep 21 2004
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