A032693 Exactly 3 digits from {1,2,3,4,5,6,7,8,9} can precede a term to form a prime.

13, 21, 23, 29, 33, 37, 43, 49, 51, 59, 61, 69, 71, 79, 81, 93, 99, 101, 103, 111, 113, 121, 127, 133, 137, 161, 163, 167, 171, 179, 181, 211, 213, 219, 253, 257, 259, 269, 271, 277, 281, 287, 293, 301, 307, 309, 319, 329, 333, 337, 343, 347, 349, 351, 361

Offset

1,1

Links

Daniel Starodubtsev, Table of n, a(n) for n = 1..10000

Example

For term 333, we find '2'333, '5'333 and '7'333 to be primes.

Mathematica

Select[Range[500], Total[Boole[PrimeQ[Table[d*10^IntegerLength[#]+#, {d, 9}]]]]==3&] (* Harvey P. Dale, Jun 30 2025 *)

Prog

(Python)
from sympy import isprime
print([i for i in range(400) if [isprime(int(j + str(i))) for j in '123456789'].count(True) == 3]) # Daniel Starodubtsev, Apr 06 2020

Crossrefs

Sequence in context: A346401 A230498 A260747 * A049745 A332512 A304006

Adjacent sequences: A032690 A032691 A032692 * A032694 A032695 A032696

Keyword

nonn,base

Author

Patrick De Geest, May 15 1998

Status

approved