cp's OEIS Frontend

A264499 Numbers n that are the product of four distinct odd primes and x^2 + y^2 = n has integer solutions.

%I A264499 #8 Dec 09 2019 13:00:01
%S A264499 32045,40885,45305,58565,67405,69745,77285,80665,91205,98345,98605,
%T A264499 99905,101065,107185,111605,114985,120445,124865,127465,128945,130645,
%U A264499 137605,141245,146705,150365,151385,162565,164645,166685,167765,173485,175565,179945,182845
%N A264499 Numbers n that are the product of four distinct odd primes and x^2 + y^2 = n has integer solutions.
%C A264499 The four primes are of the form 4*k + 1.
%H A264499 Ray Chandler, <a href="/A264499/b264499.txt">Table of n, a(n) for n = 1..10000</a> (first 1000 terms from Colin Barker)
%e A264499 32045 is in the sequence because x^2 + y^2 = 32045 = 5*13*17*29 has solutions (x,y) = (2,179), (19,178), (46,173), (67,166), (74,163), (86,157), (109,142) and (122,131).
%o A264499 (PARI)
%o A264499 dop(d, nmax) = {
%o A264499   my(L=List(), v=vector(d,m,1)~, f);
%o A264499   for(n=1, nmax,
%o A264499     f=factorint(n);
%o A264499     if(#f~==d && f[1,1]>2 && f[,2]==v && f[,1]%4==v, listput(L, n))
%o A264499   );
%o A264499   Vec(L)
%o A264499 }
%o A264499 dop(4, 200000)
%Y A264499 Cf. A131574, A264498.
%K A264499 nonn
%O A264499 1,1
%A A264499 _Colin Barker_, Nov 15 2015