References to A159698

Minimal increasing sequence beginning with 4 such that n and a(n) are either both prime or both composite.
4, 5, 7, 8, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 29, 30, 32, 33, 37, 38

2 seqfan posts