A058000 a(n) is smallest prime such that a(n)+1 is a proper multiple of a(n-1)+1 [with a(1)=1].

1, 3, 7, 23, 47, 191, 383, 1151, 6911, 27647, 138239, 691199, 3455999, 34559999, 138239999, 414719999, 2073599999, 16588799999, 364953599999, 4744396799999, 66421555199999, 132843110399999, 664215551999999, 3321077759999999