OFFSET
1,1
COMMENTS
LINKS
Clark Kimberling, Table of n, a(n) for n = 1..10000
FORMULA
a(n) ~ kn, where k = 2/(1-2/Pi) = 5.50387..., by the equidistribution theorem. - Charles R Greathouse IV, Oct 09 2016
MATHEMATICA
z = 400; f[x_] := Sin[x];
Select[Range[z], f[#] > 0 && f[# + 2] > 0 &] (* A277093 *)
Select[Range[z], f[#] > 0 && f[# + 2] < 0 &] (* A277094 *)
Select[Range[z], f[#] < 0 && f[# + 2] > 0 &] (* A277095 *)
Select[Range[z], f[#] < 0 && f[# + 2] < 0 &] (* A277096 *)
SequencePosition[Table[If[Sin[n]<0, 1, 0], {n, 400}], {1, _, 1}][[All, 1]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Aug 03 2019 *)
PROG
(PARI) is(n)=my(x=frac(n/2/Pi)); x>1/2 && x<1-1/Pi \\ Charles R Greathouse IV, Oct 09 2016
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Clark Kimberling, Oct 01 2016
STATUS
approved