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 A239396 #12 Mar 31 2014 17:40:05
%S A239396 6,8,18,12,24,30,42,36,36,66,48,66,90,72,72,102,108,114,108,108,126,
%T A239396 120,144,174,162,198,156,180,186,198,192,228,234,228,270,228,258,252,
%U A239396 252,306,300,306,288,306,330,300,336,336,372,378,390,360,402,420,438
%N A239396 Number of prime nonnegative Hurwitz quaternions having norm prime(n).
%C A239396 For n > 1, there are prime(n) + 1 more nonnegative Hurwitz quaternions than nonnegative Lipschitz quaternions. - _T. D. Noe_, Mar 31 2014
%H A239396 Wikipedia, <a href="http://en.wikipedia.org/wiki/Hurwitz_quaternion">Hurwitz quaternion</a>
%e A239396 The six prime nonnegative Hurwitz quaternions having norm 2 are 1+i, 1+j, 1+k, i+j, i+k, and j+k.
%t A239396 (* first << Quaternions` *) mx = 17; lst = Flatten[Table[{a, b, c, d}/2, {a, 0, mx}, {b, 0, mx}, {c, 0, mx}, {d, 0, mx}], 3]; q = Select[lst, Norm[Quaternion @@ #] < mx^2 && PrimeQ[Quaternion @@ #, Quaternions -> True] &]; q2 = Sort[q, Norm[#1] < Norm[#2] &]; Take[Transpose[Tally[(Norm /@ q2)^2]][[2]], mx]
%Y A239396 Cf. A239393 (prime Lipschitz quaternions).
%Y A239396 Cf. A239395 (prime Hurwitz quaternions).
%K A239396 nonn
%O A239396 1,1
%A A239396 _T. D. Noe_, Mar 21 2014