A101988 Number of primes (with repetition) that can be formed from digits of the n-th prime.

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, 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, 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

Offset

1,6

Comments

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.

Links

Table of n, a(n) for n=1..102.

Example

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.

Mathematica

(* 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 *)

Crossrefs

Cf. A039992, A045719.

Sequence in context: A324078 A068119 A039992 * A200606 A293862 A295676

Adjacent sequences: A101985 A101986 A101987 * A101989 A101990 A101991

Keyword

base,easy,nonn

Author

Zak Seidov, Jan 29 2005

Extensions

Corrected and extended by Robert G. Wilson v, Feb 10 2005

Definition clarified by Ray Chandler, Mar 01 2005

Status

approved