OFFSET
1,1
COMMENTS
a(14) has 1525 digits. - Michael S. Branicky, Jan 27 2023
LINKS
Michael S. Branicky, Table of n, a(n) for n = 1..13
MATHEMATICA
Select[Flatten[Table[10 FromDigits[PadRight[{d}, n, 2]]+d, {d, {1, 3, 7, 9}}, {n, 2, 70}]], PrimeQ]//Sort (* Harvey P. Dale, Feb 05 2023 *)
PROG
(PARI) n10np1(n, d) = { local(x, y, k); for(x=1, n, for(k=1, 9, y=10^(x+1)*k+floor(10^x*d/9)*10+k; if(isprime(y), print1(y", ")) ) ) }
(Python)
from sympy import isprime
from itertools import count, islice
def agen(): yield from (t for i in count(1) for f in "1379" if isprime(t:=int(f + "2"*i + f)))
print(list(islice(agen(), 10))) # Michael S. Branicky, Jan 27 2023
CROSSREFS
KEYWORD
easy,nonn,base
AUTHOR
Cino Hilliard, Jul 11 2005
EXTENSIONS
Name changed by Arkadiusz Wesolowski, Sep 07 2011
STATUS
approved