A131880 a(n) = the n-th positive integer which is coprime to (2^n -1). a(n) = the n-th term of row n in triangle A131879.

1, 2, 3, 7, 5, 10, 7, 14, 10, 16, 11, 31, 13, 20, 17, 31, 17, 32, 19, 46, 24, 34, 23, 62, 25, 38, 31, 56, 29, 61, 31, 62, 39, 50, 36, 97, 37, 56, 45, 97, 41, 74, 43, 86, 53, 70, 47, 122, 49, 85, 59, 98, 53, 103, 58, 122, 66, 88, 59, 173, 61, 92, 74, 127, 67, 125, 67, 127, 81