A232764 Numbers n such that the concatenation A000461(d_1)//A000461(d_2)//...//A000461(d_k) is prime, where d_i is the i-th digit of n and n is k digits long.

11, 31, 53, 101, 110, 131, 149, 159, 169, 189, 223, 231, 243, 249, 283, 297, 301, 310, 311, 313, 327, 331, 361, 381, 397, 429, 437, 453, 463, 503, 513, 530, 533, 561, 627, 641, 651, 657, 691, 779, 813, 861, 937, 941, 951, 961, 973, 1001, 1010, 1031, 1049, 1059, 1069

Offset

1,1

Comments

If one of the digits is 0, it is read "zero zeros" and the term is thus omitted from the concatenation.

There are infinitely many numbers in this sequence. Any number can have an infinite number of 0's in its decimal expansion.

Links

Table of n, a(n) for n=1..53.

Example

For n = 53, this becomes 5 fives and then 3 threes = 55555333. Since 55555333 is prime, 53 is a member of this sequence.

Prog

(Python)
import sympy
from sympy import isprime
def a():
..for n in range(1, 10**4):
....num = ''
....lst = list(str(n))
....for i in lst:
......num += i*int(i)
....if isprime(int(num)):
......print(n)
a()

Crossrefs

Cf. A000461.

Sequence in context: A152293 A031287 A230329 * A057630 A057628 A144364

Adjacent sequences: A232761 A232762 A232763 * A232765 A232766 A232767

Keyword

nonn,base

Author

Derek Orr, Jun 01 2014

Status

approved