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 A273960 #25 Jul 01 2016 11:46:52
%S A273960 -2,3,-5,7,-11,13,-17,19,-23,29,-31,37,-41,43,-47,53,-59,61,-67,71,
%T A273960 -73,79,-83,89,-97,101,-103,107,-109,113,-127,131,-137,139,-149,151,
%U A273960 -157,163,-167,173,-179,181,-191,193,-197,199,-211,223,-227,229,-233,239,-241,251,-257,263,-269,271
%N A273960 a(n) = (-1)^n*prime(n).
%F A273960 a(n) = A000040(n)*A033999(n). - _Felix Fröhlich_, Jun 15 2016
%e A273960 a(1) = 2*(-1)^1 = -2.
%e A273960 a(2) = 3*(-1)^2 = 3.
%e A273960 a(3) = 5*(-1)^3 = -5.
%t A273960 Table[Prime[n]*(-1)^n,{n,1,70}]
%t A273960 Table[If[OddQ[n],-Prime[n],Prime[n]],{n,70}] (* _Harvey P. Dale_, Jul 01 2016 *)
%o A273960 (PARI) a(n) = prime(n)*(-1)^n \\ _Felix Fröhlich_, Jun 15 2016
%Y A273960 Cf. A000040, A083236.
%K A273960 sign
%O A273960 1,1
%A A273960 _Terry D. Grant_, Jun 12 2016