A004083 a(n) = n-th positive integer k such that cos(k-1) <= 0 and cos(k) > 0.

1, 5, 11, 18, 24, 30, 37, 43, 49, 55, 62, 68, 74, 81, 87, 93, 99, 106, 112, 118, 125, 131, 137, 143, 150, 156, 162, 169, 175, 181, 187, 194, 200, 206, 213, 219, 225, 231, 238, 244, 250, 257, 263, 269, 275, 282, 288, 294