OFFSET
1,2
COMMENTS
The sequence would be tragically short were the '1' not there.
From Robert Israel, Dec 04 2019: (Start)
There are 5 terms with 1 digit, 9 with 2 digits, 12 with 4 digits, 15 with 8 digits, 15 with 16 digits, 7 with 32 digits, and only 1 with 64 digits, which must be the last term. (End)
LINKS
Robert Israel, Table of n, a(n) for n = 1..64
EXAMPLE
11231723 is there because it is prime and 1123 and 1723 are there.
MAPLE
R[0]:= [1, 2, 3, 5, 7]:
for m from 1 do
R[m]:= select(isprime, [seq(seq(10^(2^(m-1))*a+b, b=R[m-1]), a=R[m-1])]);
until R[m] = []:
seq(op(R[i]), i=1..m-1); # Robert Israel, Dec 04 2019
MATHEMATICA
L = t = {1, 2, 3, 5, 7}; While[t != {}, t = Select[FromDigits /@ Join @@@ IntegerDigits /@ Tuples[t, 2], PrimeQ]; L = Join[L, t]]; L (* Giovanni Resta, Dec 05 2019 *)
CROSSREFS
KEYWORD
nonn,base,fini,full
AUTHOR
Roger L. Bagula, Nov 27 2004
EXTENSIONS
Edited by N. J. A. Sloane, Nov 10 2005
Offset changed by Robert Israel, Dec 04 2019
STATUS
approved