A050091 a(n) = n-th number k such that b(k)>b(k+1), where b=A050088.

2, 4, 6, 8, 9, 11, 12, 15, 17, 19, 21, 22, 23, 25, 26, 27, 29, 31, 32, 36, 38, 40, 42, 43, 44, 46, 47, 48, 50, 51, 53, 54, 56, 57, 59, 61, 62, 64, 66, 67, 69, 70, 72, 74, 75, 76, 78, 80, 81, 83, 85, 86, 87, 89, 91, 93, 94, 96, 98, 100, 101