1,1

Apparently there are no such primes > 373.

Comments from Jean-Marc Falcoz (jeanmarcfalcoz(AT)vtxnet.ch), Jan 11 2009: This is correct.

There can't be any more terms, because they must necessarily be of the form

23737373733737... but the substring 237 is composite

or 273737373... but 273 is composite

or 5373737373... but 537 is composite

or 5737373737... but 573 is composite

or 37373737373... but 3737 is composite

or 7373737373... but 737 is composite

No other form is possible, otherwise, if the digit 2 or 5 is anywhere inside

or at the end of the number, one substring-number is even or divisible by 5,

and furthermore, there can't be twin digits, because one substring-number

would then be divisible by 11.

Obviously, the digits 0, 1, 4, 6, 8, 9 can't appear anywhere in a term of the sequence.

Example : 373 is in the sequence, because 3, 7, 37, 73 and 373 are prime,

but 733 is not in the sequence, because 33 isn't prime.

Cf. A085822.

Sequence in context: A096148 A124674 A020994 this_sequence A100552 A155873 A106711

Adjacent sequences: A085820 A085821 A085822 this_sequence A085824 A085825 A085826

full,nonn,fini,base

Zak Seidov (zakseidov(AT)yahoo.com), Jul 04 2003

Thanks to Mark Underwood for pointing out misprints in the first version of this sequence.

Edited by N. J. A. Sloane, Jun 20 2009 at the suggestion of Lekraj Beedassy (blekraj(AT)yahoo.com)