A154865 Numbers n such that smallest digit of n is prime and the smallest digit of prime(n) is also prime.

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

Links

Table of n, a(n) for n=1..56.

Example

If prime(n=2)=3, 2=prime and 3=prime, then 2=a)1). If prime(n=3)=5, 3=prime and 5=prime, then 3=a(2). If prime(n=22)=79, 2=2=prime and 9>7=prime, then 22=a(3). If prime(n=23)=83, 3>2=prime and 8>3=prime, then 23=a(4). If prime(n=25)=97, 5>2=prime and 9>7=prime, then 25=a(5). If prime(n=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

Cf. A000027, A000040.

Sequence in context: A084796 A084797 A163902 * A032810 A248907 A062921

Adjacent sequences: A154862 A154863 A154864 * A154866 A154867 A154868

Keyword

nonn,base

Author

Juri-Stepan Gerasimov, Jan 16 2009

Extensions

335 replaced by 334, keyword:base added - R. J. Mathar, Mar 29 2010

Status

approved