A069612 a(1) = 19 (the smallest prime ending in a 9) and a(n+1) = smallest prime ending in a(n).

19, 419, 5419, 35419, 435419, 11435419, 111435419, 9111435419, 89111435419, 1389111435419, 81389111435419, 381389111435419, 15381389111435419, 3315381389111435419, 153315381389111435419, 22153315381389111435419, 2022153315381389111435419

Offset: 1

Author

Amarnath Murthy, Mar 27 2002

Keywords

• nonn
• base

Links

• Michael S. Branicky, Table of n, a(n) for n = 1..367 (terms 1..300 from Harvey P. Dale)

Crossrefs

Cf. A053582, A053583, A053584.

Programs

Mathematica

w=9; Table[w; i=1; While[PrimeQ[ToExpression[StringJoin[ToString[i], ToString[w]]]]==False, i++ ]; w=ToExpression[StringJoin[ToString[i], ToString[w]]], {32}]
nxt[n_]:=Module[{c=10^IntegerLength[n],x=1},While[!PrimeQ[c*x+n],x++];c*x+n]; NestList[nxt,19,15] (* Harvey P. Dale, Sep 25 2013 *)

Python

from sympy import isprime
from itertools import count, islice
def agen(an=19):
    while True:
        yield an
        pow10 = 10**len(str(an))
        for t in count(pow10+an, step=pow10):
            if isprime(t):
                an = t
                break
print(list(islice(agen(), 17))) # Michael S. Branicky, Jun 23 2022

Extensions

More terms from Hans Havermann, Jun 06 2002