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A154865
Numbers k such that smallest digit of k is prime and the smallest digit of prime(k) is also prime.
0
2, 3, 22, 23, 25, 52, 55, 56, 57, 59, 62, 72, 73, 75, 77, 78, 85, 332, 333, 334, 336, 337, 338, 342, 345, 346, 348, 352, 354, 355, 356, 357, 363, 364, 365, 366, 367, 372, 373, 375, 376, 378, 382, 383, 384, 385, 386, 388, 389, 392, 393, 398, 423, 424, 425, 426
OFFSET
1,1
EXAMPLE
If prime(k=2)=3, 2=prime and 3=prime, then 2=a(1).
If prime(k=3)=5, 3=prime and 5=prime, then 3=a(2).
If prime(k=22)=79, 2=2=prime and 9>7=prime, then 22=a(3).
If prime(k=23)=83, 3>2=prime and 8>3=prime, then 23=a(4).
If prime(k=25)=97, 5>2=prime and 9>7=prime, then 25=a(5).
If prime(k=52)=239, 5>2=prime and 9>3>2=prime, then 52=a(6), etc.
MATHEMATICA
Select[Range[500], AllTrue[{Min[IntegerDigits[#]], Min[ IntegerDigits[ Prime[#]]]}, PrimeQ]&] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, Sep 20 2018 *)
CROSSREFS
Sequence in context: A084796 A084797 A163902 * A032810 A248907 A062921
KEYWORD
nonn,base
AUTHOR
EXTENSIONS
335 replaced by 334, keyword:base added - R. J. Mathar, Mar 29 2010
STATUS
approved