A101988 - OEIS

%I #9 Feb 15 2015 16:07:33

%S 1,1,1,1,1,3,3,1,3,2,3,4,1,2,2,3,2,1,2,3,4,3,2,1,3,3,7,8,3,9,6,9,11,6,

%T 6,3,7,7,8,11,10,3,5,6,10,5,3,6,4,5,6,6,4,4,4,4,3,6,5,3,6,6,9,9,8,11,

%U 8,10,8,4,6,7,7,10,10,5,6,10,3,1,6,4,6,5,4,4,1,5,4,4,5,6,3,6,1,7,5,4,6,3,5,4

%N Number of primes (with repetition) that can be formed from digits of the n-th prime.

%C Here we put all the digits of prime(n) into a bag and ask how many not necessarily distinct primes can be formed using some or all of these digits.

%e a(35)=6 because from the digits of p(35)=149, six numbers can be formed, 19, 41, 149, 419, 491 & 941, which are primes.

%t (* first do *) Needs["DiscreteMath`Combinatorica`"] (* then *) f[n_] := Length[ Select[ FromDigits /@ Flatten[ Permutations /@ Subsets[ IntegerDigits[ Prime[n]]], 1], PrimeQ[ # ] &] ]; Table[ f[n], {n, 102}] (* _Robert G. Wilson v_, Feb 10 2005 *)

%Y Cf. A039992, A045719.

%K base,easy,nonn

%O 1,6

%A _Zak Seidov_, Jan 29 2005

%E Corrected and extended by _Robert G. Wilson v_, Feb 10 2005

%E Definition clarified by _Ray Chandler_, Mar 01 2005