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 A078908 #14 Feb 28 2020 08:39:57 %S A078908 0,2,3,4,3,5,7,6,6,5,11,7,5,9,6,8,5,8,19,7,10,13,23,9,6,7,9,11,7,8,31, %T A078908 10,14,7,10,10,7,21,8,9,9,12,43,15,9,25,47,11,14,8,8,9,9,11,14,13,22, %U A078908 9,59,10,11,33,13,12,8,16,67,9,26,12,71,12,11,9,9,23,18,10,79,11,12,11 %N A078908 Let r+i*s be the sum, with multiplicity, of the first-quadrant Gaussian primes dividing n; sequence gives r values (with a(1) = 0). %C A078908 A Gaussian integer z = x+iy is in the first quadrant if x > 0, y >= 0. Just one of the 4 associates z, -z, i*z, -i*z is in the first quadrant. %C A078908 The sequence is fully additive. %H A078908 Amiram Eldar, <a href="/A078908/b078908.txt">Table of n, a(n) for n = 1..10000</a> %H A078908 Michael Somos, <a href="/A078458/a078458.txt">PARI program for finding prime decomposition of Gaussian integers</a> %H A078908 <a href="/index/Ga#gaussians">Index entries for Gaussian integers and primes</a> %e A078908 5 factors into the product of the primes 1+2*i, 1-2*i, but the first-quadrant associate of 1-2*i is i*(1-2*i) = 2+i, so r+i*s = 1+2*i + 2+i = 3+3*i. Therefore a(5) = 3. %t A078908 a[n_] := Module[{f = FactorInteger[n, GaussianIntegers->True]}, p = f[[;;,1]]; e = f[[;;,2]]; Re[Plus @@ ((If[Abs[#] == 1, 0, #]& /@ p) * e)]]; Array[a, 100] (* _Amiram Eldar_, Feb 28 2020 *) %Y A078908 Cf. A078458, A078909, A078910, A078911, A080088, A080089. %K A078908 nonn,easy %O A078908 1,2 %A A078908 _N. J. A. Sloane_, Jan 11 2003 %E A078908 More terms and information from _Vladeta Jovovic_, Jan 27 2003