A088266 Smallest number that yields a prime when concatenated with A088265(k) for all k <= n.

2, 3, 3, 189, 210, 31296, 105441, 105441, 46814571, 665216481, 111581348556, 1199096907504

Offset: 1

Author

Amarnath Murthy, Sep 28 2003

Keywords

• base
• nonn
• fini
• full

Comments

a(n) == 0 (mod 3) for n > 1.

a(n) <> 4 (mod 7) and a(n) <> 9 (mod 11) for n > 2 (where <> means "not equal"). - M. F. Hasler, Oct 15 2012

Terms a(13) onward do not exist as at least one of the corresponding concatenations is always divisible by 7. - Max Alekseyev, Oct 14 2012

Examples

			a(1) = 2 since 211 is prime.
a(4) = 189 since 18911, 18913, 18917 and 18919 are all prime.
		

Crossrefs

Cf. A088265, A088267.

Programs

PARI

A088266(n)=for(t=1,9e9,for(k=1,n,isprime(t*10^((k+7)\4)+A088265(k))||next(2));return(t))  \\ Only useful for n<9. - M. F. Hasler, Oct 15 2012

Extensions

More terms from David Wasserman, Jul 27 2005

a(10..12) from Don Reble, Oct 15 2012

a(10..12) confirmed by D. S. McNeil, Oct 16 2012