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 A078613 #19 Jul 12 2024 21:54:11
%S A078613 1,2,4,8,15,16,30,32,35,39,45,51,55,60,64,70,75,78,87,90,91,95,102,
%T A078613 110,111,115,117,119,120,123,128,135,140,143,150,153,155,156,159,174,
%U A078613 175,180,182,183,187,190,203,204,215,219,220,222,225,230,234,235,238,240
%N A078613 Same numbers of distinct prime factors of forms 4*k+1 and 4*k+3.
%C A078613 Equivalently, numbers n such that A005089(n)=A005091(n); A005094(a(n))=0.
%C A078613 A001221(a(n)) and a(n) are of opposite parity.
%C A078613 If m is in the sequence, then also 2*m.
%C A078613 Conjecture : a(n) is asymptotic to c*n where c is around 4 - _Benoit Cloitre_, Jan 06 2003
%H A078613 Reinhard Zumkeller, <a href="/A078613/b078613.txt">Table of n, a(n) for n = 1..10000</a>
%e A078613 n = 99 = [(4*0+3)^2]*[(4*1+1)], therefore 99 is a term.
%t A078613 fQ[n_]:=Plus@@((Mod[#[[1]],4]-2)&/@If[n==1,{},FactorInteger[n]])==0; Select[Range[240],fQ] (* Ray Chandler, Dec 18 2011*)
%o A078613 (Haskell)
%o A078613 a078613 n = a078613_list !! (n-1)
%o A078613 a078613_list = filter ((== 0) . a005094) [1..]
%o A078613 -- _Reinhard Zumkeller_, Jan 07 2013
%Y A078613 Cf. A072202.
%Y A078613 Cf. A221264, A221265.
%K A078613 nonn
%O A078613 1,2
%A A078613 _Reinhard Zumkeller_, Dec 10 2002
%E A078613 Edited by _Ray Chandler_, Dec 18 2011