|
|
A032685
|
|
Numbers k such that k surrounded by digit '9' is a prime.
|
|
8
|
|
|
1, 2, 10, 19, 20, 23, 31, 34, 41, 43, 47, 53, 61, 62, 64, 67, 68, 71, 73, 74, 76, 82, 83, 85, 92, 94, 100, 101, 107, 109, 112, 113, 115, 119, 122, 124, 130, 136, 145, 149, 152, 163, 190, 193, 196, 200, 211, 217, 218, 221, 226, 236, 239, 241, 245
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,2
|
|
LINKS
|
|
|
MATHEMATICA
|
Select[Range[300], PrimeQ[FromDigits[Join[{9}, IntegerDigits[#], {9}]]]&] (* Harvey P. Dale, Jul 20 2012 *)
|
|
PROG
|
(Python)
from sympy import isprime
def ok(n): return isprime(int('9' + str(n) + '9'))
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,base
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|