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A089323 Smallest k such that concatenation of r*k and 1 is a prime for all r = 1 to n, or smallest k such that 10*r*k +1 is a prime for all r = 1 to n. 2

%I

%S 1,3,21,33,1083,2541,51282,51282,1296060612,43449172767,189324538095

%N Smallest k such that concatenation of r*k and 1 is a prime for all r = 1 to n, or smallest k such that 10*r*k +1 is a prime for all r = 1 to n.

%C The primes arising in triangular form are

%C 11

%C 31 61

%C 211 421 631

%C 331 661 991 1321

%C ...

%C Next term is > 1.38*10^12. - _David Wasserman_, Sep 13 2005

%K base,hard,nonn

%O 1,2

%A _Amarnath Murthy_, Nov 03 2003

%E More terms from _Ray G. Opao_, Jan 13 2005

%E 3 more terms from _David Wasserman_, Sep 13 2005

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Last modified September 30 13:02 EDT 2022. Contains 357105 sequences. (Running on oeis4.)