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A068687
Primes which are a sandwich of numbers made of only one digit between two 3's.
3
313, 353, 373, 383, 3222223, 3444443, 322222223, 355555553, 3111111111113, 3444444444443, 3888888888883, 311111111111113, 377777777777773, 3111111111111111111111111111113, 3888888888888888888888888888883
OFFSET
1,1
COMMENTS
a(36) has 1065 digits. - Michael S. Branicky, Jan 28 2023
LINKS
Michael S. Branicky, Table of n, a(n) for n = 1..35
PROG
(Python)
from sympy import isprime
from itertools import count, islice
def agen(): yield from (t for i in count(1) for m in "124578" if isprime(t:=int("3" + m*i + "3")))
print(list(islice(agen(), 20))) # Michael S. Branicky, Jan 28 2023
CROSSREFS
Cf. A068685.
Sequence in context: A061323 A082584 A088282 * A093808 A257527 A142745
KEYWORD
base,nonn
AUTHOR
Amarnath Murthy, Mar 02 2002
EXTENSIONS
More terms from Sascha Kurz, Mar 17 2002
STATUS
approved