%I #14 Jun 25 2019 06:09:41
%S 2,4,12,60,60,120,360,3960,27720,27720,27720,27720,27720,637560,
%T 8288280,240360120,240360120,240360120,240360120,240360120,240360120,
%U 9854764920,9854764920,19709529840,98547649200,1675310036400,88791431929200
%N Smallest number m with property that 2^m-1 is divisible by first n odd primes.
%H T. D. Noe, <a href="/A155747/b155747.txt">Table of n, a(n) for n = 1..500</a>
%F 2^m == 1 (mod (primorial(n)/2)) == 1 (mod (A002110(n+1)/2)).
%e n=1, m=2, 2^2-1=3;
%e n=2, m=4, 2^4-1=15=3*5;
%e n=3, m=12, 2^12-1=4095=(3*5*7)*39;
%e n=4, m=60, 2^60-1=1152921504606846975=(3*5*7*11)*998200436889045;
%e n=5, m=60, 2^60-1=1152921504606846975=(3*5*7*11*13)*76784648991465;
%e n=6, m=120, 2^120-1=1329227995784915872903807060280344575=(3*5*7*11*13*17)*5207451355644026063755096120665.
%t Table[LCM@@(MultiplicativeOrder[2,# ]& /@ Prime[Range[2,n]]), {n,2,50}] (* _T. D. Noe_, May 07 2010 *)
%o (PARI) a(n) = lcm(vector(n, k, znorder(Mod(2, prime(k+1))))); \\ _Michel Marcus_, Jun 25 2019
%Y Cf. A002110.
%K nonn
%O 1,1
%A _Zak Seidov_, Jan 26 2009
%E a(16)-a(21) from _D. S. McNeil_, Mar 04 2009
%E Extended by _T. D. Noe_, May 07 2010