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Primes written with prime number of Roman numerals.
0

%I #12 May 13 2013 01:49:56

%S 2,3,7,11,19,23,41,43,47,59,61,67,79,83,97,101,109,113,131,137,149,

%T 151,157,173,199,223,227,239,241,263,281,293,311,313,317,331,349,353,

%U 401,419,421,439,443,461,463,467,479,491,509,557,569,571,577,599,601,607,619,641,643,647

%N Primes written with prime number of Roman numerals.

%t Select[Prime[Range[200]],PrimeQ[Length[Characters[IntegerString[#, "Roman"]]]]&] (* _Harvey P. Dale_, Mar 19 2013 *)

%o (PARI) Roman(n)=my(s);while(n,s+=[0,1,2,3,2,1,2,3,4,2][n%10+1];n\=10);s

%o forprime(p=2,3999,if(isprime(Roman(p)),print1(p", "))) \\ _Charles R Greathouse IV_, Oct 06 2011

%Y Cf. A003587, A195526.

%K nonn,base

%O 1,1

%A _Juri-Stepan Gerasimov_, Sep 21 2011