A211682 Prime numbers such that all the substrings of length <= 2 are primes.

2, 3, 5, 7, 23, 37, 53, 73, 373, 237373, 537373, 5373737, 53737373, 53737373737, 237373737373, 737373737373737, 53737373737373737, 373737373737373737373, 53737373737373737373737, 53737373737373737373737373, 373737373737373737373737373, 5373737373737373737373737373737

Offset: 1

Author

Hieronymus Fischer, Apr 30 2012

Keywords

• nonn
• base

Comments

A211681 restricted to primes. Contains A085823. In contrast to A085823 this sequence seems to be not finite (conjecture).

Examples

			a(10)=237373, since all substrings of length <= 2 are primes (2, 3, 7, 23, 37, 73) and 237373 is prime.
		

Links

• Giovanni Resta, Table of n, a(n) for n = 1..36 (terms < 10^1000)

Crossrefs

Cf. A085823, A019546, A046034, A211681.

Extensions

The originally submitted terms with index 20 and 21 are composite and have been erased therefore. - Hieronymus Fischer, Sep 24 2018

a(20)-a(22) from Giovanni Resta, Oct 08 2018