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 A327423 #8 Nov 30 2019 01:55:35
%S A327423 2,3,5,6,8,9,11,12,15,18,21,24,25,27,28,30,31,33,34,37,40,43,46,47,49,
%T A327423 50,52,53,55,56,59,62,65,68,69,71,72,74,75,77,78,81,84,87,90,91,93,94,
%U A327423 96,97,99,100,103,106,109,112,113,115,116,118,119,121,122,125,128
%N A327423 Positive integers k such that tan(k) < 0 (or equivalently, cot(k) < 0).
%C A327423 Complement of A327422.
%C A327423 Numbers k such that 1/2 < {k/Pi} < 1, where {} is the fractional part.
%C A327423 Numbers k such that A330035(k) = -1.
%C A327423 Also positive integers k such that sin(2k) < 0, i.e., k such that 2k is in A070751.
%t A327423 upto[n_] := Select[Range[n], Tan[#] < 0 &]
%o A327423 (PARI) A327423_up_to_n(n) = my(v=vector(n,k,k)); select(k->tan(k)<0,v)
%Y A327423 Cf. A330035.
%Y A327423 Cf. A070752 (sin(k) > 0 or csc(k) > 0), A070751 (sin(k) < 0 or csc(k) < 0), A131503 (cos(k) > 0 or sec(k) > 0), A327422 (tan(k) > 0 or cot(k) > 0), this sequence (tan(k) < 0 or cot(k) < 0).
%K A327423 nonn
%O A327423 1,1
%A A327423 _Jianing Song_, Nov 29 2019