Beginning with 7, primes of the form: least multiple of the previous term followed by a 1. Beginning with 7, a(n) is the least prime of the form k*a(n-1)*10 +1.
nxt[n_]:=Module[{k=1}, While[CompositeQ[10*k*n+1], k++]; 10*k*n+1]; NestList[ nxt, 7, 20] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Aug 04 2019 *)
