OFFSET
1,1
COMMENTS
Conjecture: sequence is infinite. Notes: (1) If n==1 (mod 3) then in most cases a(n) is a permutation of (n-1), 1's and a 7, else a(n) is a digit permutation of (n-1) ones and a 3; (2) Obviously all the digits except the most significant one must be odd.
The least potential candidate, lpc(n), is of the form (10^n-1)/9. The following is a(n)-lpc(n): 1, 0, 2, 6, 2, 8, 268, 6, 2, 862, 2, 268, 606, 608, 602, 208, 8, 20, 0, 20, 68, 600, 0, 2, 606, .... - Robert G. Wilson v, May 12 2014
LINKS
Robert G. Wilson v, Table of n, a(n) for n = 1..100
EXAMPLE
a(5) = 11113 in which 11,11,11,13 are the two-digit string primes.
MATHEMATICA
fQ[p_] := Block[{id = IntegerDigits@ p}, Union@ PrimeQ[ FromDigits@# & /@ Partition[id, 2, 1]] == {True}]; f[n_] := Block[{p = NextPrime[(10^n - 1)/9 - 1]}, While[! fQ@ p, p = NextPrime@ p]; p]; f[1] = 2; Array[ f, 19] (* Robert G. Wilson v, May 12 2014 *)
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Amarnath Murthy, Dec 08 2003
EXTENSIONS
More terms from David Wasserman, Dec 21 2005
STATUS
approved