This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A325073 #14 Apr 12 2019 08:25:27 %S A325073 29,89,229,349,509,709,769,809,1009,1049,1109,1229,1249,1289,1409, %T A325073 1549,1669,1709,1789,2029,2069,2089,2389,2729,3049,3089,3169,3329, %U A325073 3389,3469,3529,3929,3989,4049,4229,4289,4549,4649,4729,4789,5009,5209,5669,5689,5849 %N A325073 Prime numbers congruent to 9 modulo 20 representable by x^2 + 20*y^2. %C A325073 Brink showed that prime numbers congruent to 9 modulo 20 are representable by exactly one of the quadratic forms x^2 + 20*y^2 or x^2 + 100*y^2. This sequence corresponds to those representable by the first form, and A325074 corresponds to those representable by the second form. %H A325073 David Brink, <a href="https://doi.org/10.1016/j.jnt.2008.04.007">Five peculiar theorems on simultaneous representation of primes by quadratic forms</a>, Journal of Number Theory 129(2) (2009), 464-468, doi:10.1016/j.jnt.2008.04.007, MR 2473893. %H A325073 Rémy Sigrist, <a href="/A325073/a325073.gp.txt">PARI program for A325073</a> %H A325073 Wikipedia, <a href="https://en.wikipedia.org/wiki/Kaplansky%27s_theorem_on_quadratic_forms">Kaplansky's theorem on quadratic forms</a> %e A325073 Regarding 1009: %e A325073 - 1009 is a prime number, %e A325073 - 1009 = 50*20 + 9, %e A325073 - 1009 = 17^2 + 20*6^2, %e A325073 - hence 1009 belongs to this sequence. %o A325073 (PARI) See Links section. %Y A325073 See A325067 for similar results. %Y A325073 Cf. A141883, A325074. %K A325073 nonn %O A325073 1,1 %A A325073 _Rémy Sigrist_, Mar 27 2019