%I #10 Oct 19 2017 03:14:24

%S 3,3,4,6,6,154770,2894220,2894220,407874180,214580145780,

%T 9448481062020,247236503934420,2545206711847800,18178612369988250180,

%U 53792264108455702830

%N a(n) = smallest number k such that rk-1 is prime for all r = 1 to n.

%C Is the sequence finite?

%H Carlos Rivera, <a href="http://www.primepuzzles.net/puzzles/puzz_379.htm">Problems & Puzzles</a>.

%e a(5)=6 because 1*6-1, 2*6-1, 3*6-1, 4*6-1, 5*6-1 are all prime.

%e a(11)=9448481062020 because all eleven numbers 1*9448481062020-1, 2*9448481062020-1,3*9448481062020-1,...,10*9448481062020-1 & 11*9448481062020-1 are prime and 9448481062020 is the smallest number with such property.

%Y Cf. A088652, A125838, A125839, A088250, A101779.

%K nonn

%O 1,1

%A _Amarnath Murthy_, Oct 29 2003

%E Corrected and extended by _Ray Chandler_, Nov 01 2003

%E More terms from _Don Reble_, Nov 23 2003

%E Entry revised by _N. J. A. Sloane_, Jan 05 2007

%E a(14)-a(15) from _Jens Kruse Andersen_, May 02 2008