A375261 Smallest n-digit reversible prime with only prime digits.

2, 37, 337, 3257, 32233, 322573, 3222223, 32235223, 322222223, 3222222257, 32222232577, 322222232537, 3222222223333, 32222222332733, 322222222237537, 3222222222223373, 32222222222223353, 322222222222225333, 3222222222222222577, 32222222222222225573, 322222222222222233253

Offset

1,1

Links

Table of n, a(n) for n=1..21.

Formula

a(n) <= A177513(n) for n > 1.

if a(n) is not a palindrome, a(n) = A177513(n) for n > 1.

Prog

(Python)
from sympy import isprime
from itertools import product
def a(n):
    if n == 1: return 2
    for first in "37":
        for rest in product("2357", repeat=n-1):
            s = first + "".join(rest)
            if isprime(t:=int(s)) and isprime(int(s[::-1])):
                return t
print([a(n) for n in range(1, 22)]) # Michael S. Branicky, Aug 08 2024

Crossrefs

Cf. A006567, A177513.

Sequence in context: A200911 A243101 A001569 * A373618 A092853 A297796

Adjacent sequences: A375258 A375259 A375260 * A375262 A375263 A375264

Keyword

base,nonn

Author

Jean-Marc Rebert, Aug 08 2024

Status

approved