A081835 a(1)=1, a(n)=a(n-1)+5 if n is already in the sequence, a(n)=a(n-1)+4 otherwise.

1, 5, 9, 13, 18, 22, 26, 30, 35, 39, 43, 47, 52, 56, 60, 64, 68, 73, 77, 81, 85, 90, 94, 98, 102, 107, 111, 115, 119, 124, 128, 132, 136, 140, 145, 149, 153, 157, 162, 166, 170, 174, 179, 183, 187, 191, 196, 200, 204, 208, 212, 217, 221, 225, 229, 234, 238, 242