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A104388 Lesser of two successive primes the average of which is a repdigit. 5
3, 5, 7, 97, 109, 4441, 111111109, 555555555551, 9999999999999937, 111111111111111091, 444444444444444419, 555555555555555555491, 777777777777777777777767, 333333333333333333333333333333293, 444444444444444444444444444444444391 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
FORMULA
a(n) = prime(A104386(n)).
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 p
print(list(islice(agen(), 15))) # Michael S. Branicky, Jun 30 2022
CROSSREFS
Cf. A054268, A104386, A104387 (larger primes), A104389 (repdigits).
Sequence in context: A082697 A051345 A242387 * A110337 A132287 A046201
KEYWORD
nonn,base
AUTHOR
Zak Seidov, Mar 04 2005
EXTENSIONS
More terms from Giovanni Resta, Feb 09 2006
STATUS
approved

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Last modified May 26 01:11 EDT 2024. Contains 372806 sequences. (Running on oeis4.)