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A057628
Primes such that replacing each digit d with d copies of the digit d produces a prime. Zeros are not allowed.
4
11, 31, 53, 131, 149, 223, 283, 311, 313, 331, 397, 463, 641, 691, 937, 941, 1439, 1511, 1741, 1871, 1949, 1993, 1999, 2111, 2447, 2939, 3163, 3391, 3433, 3499, 3559, 3593, 3659, 3911, 3931, 5227, 5399, 5923, 6163, 6269, 6653, 6719, 7177, 7741, 8389
OFFSET
1,1
COMMENTS
"Replacing each digit d with d copies of the digit d" is the function A048376. Therefore this is the largest subset of A038618 stable under the map A048376.
EXAMPLE
E.g. 641 becomes 66666644441 which is also prime.
MATHEMATICA
Select[Prime[Range[1500]], PrimeQ[FromDigits[Flatten[Table[#, {#}]&/@ IntegerDigits[#]]]]&&DigitCount[#, 10, 0]==0&] (* Harvey P. Dale, Mar 27 2011 *)
PROG
(PARI) is_A057628(n)={vecmin(digits(n)) && is_A057630(n)} \\ M. F. Hasler, Jan 23 2013
CROSSREFS
KEYWORD
nonn,base,nice,easy
AUTHOR
G. L. Honaker, Jr., Oct 10 2000
EXTENSIONS
More terms from Patrick De Geest, Oct 15 2000.
Offset changed to 1, according to OEIS conventions, by M. F. Hasler, Jan 23 2013
STATUS
approved