A154981 Primes with nonprime smallest digit.
11, 13, 17, 19, 31, 41, 47, 61, 67, 71, 89, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 241, 251, 271, 281, 307, 311, 313, 317, 331, 401, 409, 419, 421, 431, 449, 457, 461, 467, 479, 487, 491
Offset: 1
Examples
17 is in the sequence because its smallest digit is 1, which is not prime. 19 is in the sequence because its smallest digit is 1, which is not prime (neither is 9, for that matter). 23 is not in the sequence because both of its digits are prime.
Links
- Vincenzo Librandi, Table of n, a(n) for n = 1..1000
Programs
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Mathematica
Select[Prime[Range[150]], Not[PrimeQ[Min[IntegerDigits[#]]]] &] (* Alonso del Arte, Mar 28 2014, based on Harvey P. Dale's program for A155053 *)
Extensions
Entries checked by R. J. Mathar, Mar 29 2010
Comments