A088266 - OEIS

%I #35 Nov 24 2019 02:37:38

%S 2,3,3,189,210,31296,105441,105441,46814571,665216481,111581348556,

%T 1199096907504

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

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

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

%C 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

%e a(1) = 2 since 211 is prime.

%e a(4) = 189 since 18911, 18913, 18917 and 18919 are all prime.

%o (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

%Y Cf. A088265, A088267.

%K base,nonn,fini,full

%O 1,1

%A _Amarnath Murthy_, Sep 28 2003

%E More terms from _David Wasserman_, Jul 27 2005

%E a(10..12) from _Don Reble_, Oct 15 2012

%E a(10..12) confirmed by _D. S. McNeil_, Oct 16 2012