a(n) is the n-th nonnegative integer k satisfying |sin(k)| < |cos(k)| < |sin(k+1)|.

Terms

a(0) =7a(1) =10a(2) =13a(3) =16a(4) =29a(5) =32a(6) =35a(7) =38a(8) =51a(9) =54a(10) =57a(11) =60a(12) =73a(13) =76a(14) =79a(15) =82a(16) =95a(17) =98a(18) =101a(19) =104a(20) =117a(21) =120a(22) =123a(23) =126a(24) =139a(25) =142a(26) =145a(27) =148a(28) =161a(29) =164