OFFSET
1,1
COMMENTS
The next term is 444444444444444444444444444444444497. The first term with more than 100 digits is a(22) which has 109 digits. - Harvey P. Dale, Jun 28 2011
LINKS
Michael S. Branicky, Table of n, a(n) for n = 1..31
FORMULA
a(n) = prime(A104386(n)+1).
MATHEMATICA
Union[Flatten[Table[NextPrime/@Select[FromDigits/@Table[PadLeft[{i}, n, i], {n, 45}], Mean[{NextPrime[#], NextPrime[#, -1]}]==#&], {i, 9}]]] (* Harvey P. Dale, Jun 28 2011 *)
PROG
(Python)
from itertools import count, islice
from sympy import isprime, prevprime
def agen():
for d in count(1):
ru = int("1"*d)
for r in range(ru, 10*ru, ru):
if r > 2:
p = prevprime(r)
if isprime(r + (r-p)) and prevprime(r+(r-p)) == p:
yield 2*r - p
print(list(islice(agen(), 15))) # Michael S. Branicky, Jun 30 2022
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Zak Seidov, Mar 04 2005
EXTENSIONS
More terms from Giovanni Resta, Apr 05 2006
STATUS
approved