OFFSET
1,4
LINKS
Jean-François Alcover, Table of n, a(n) for n = 1..10000
MATHEMATICA
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];
Array[a, 100] (* Jean-François Alcover, Nov 18 2021 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Sep 21 2004
STATUS
approved