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 A270370 #14 Mar 20 2016 12:40:19
%S A270370 0,-1,0,-1,0,-1,0,-1,1,-1,1,-1,1,-1,1,-1,1,-1,1,-1,1,-1,1,-1,1,-1,1,
%T A270370 -2,1,-2,1,-2,1,-2,1,-2,1,-2,1,-2,1,-2,1,-2,1,-2,1,-2,1,-2,1,-2,1,-2,
%U A270370 1,-2,1,-2,1,-2,1,-2,1,-2,2,-2,2,-2,2,-2
%N A270370 a(n) = Sum_{k=0..n} (-1)^k*floor(k^(1/3)).
%F A270370 a(n) = floor(n^(1/3))*(-1)^n/2 - ((-1)^(floor(n^(1/3))+1)+1)/4.
%e A270370 a(5) = [0^(1/3)]-[1^(1/3)]+[2^(1/3)]-[3^(1/3)]+[4^(1/3)]-[5^(1/3)] = 0-1+1-1+1-1 = -1, letting [] denote the floor function.
%t A270370 Print[Table[Sum[(-1)^i*Floor[i^(1/3)],{i,0,n}],{n,0,100}]]
%o A270370 (PARI) a(n)=sum(i=0,n,(-1)^i*sqrtnint(i,3))
%o A270370 (PARI) a(n)=sqrtnint(n,3)*(-1)^n/2-((-1)^(sqrtnint(n,3)+1)+1)/4
%Y A270370 Cf. A268173, A022554, A031876, A032512, A032513, A032514, A032515, A032516, A032517, A032518, A032519, A032520, A032521.
%K A270370 sign,easy
%O A270370 0,28
%A A270370 _John M. Campbell_, Mar 15 2016