Search: id:A155747
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%I A155747
%S A155747 2,4,12,60,60,120,360,3960,27720,27720,27720,27720,27720,637560,8288280,
%T A155747 240360120,240360120,240360120,240360120,240360120,240360120
%N A155747 Smallest number m with property that 2^m-1 is divisible by first n odd 
               primes.
%F A155747 2^m == 1 (mod (primorial(n)/2)) == 1 (mod (A002110(n+1)/2))
%e A155747 n=1, m=2, 2^2-1=3
%e A155747 n=2, m=4, 2^4-1=15=3*5
%e A155747 n=3, m=12, 2^12-1=4095=(3*5*7)*39
%e A155747 n=4, m=60, 2^60-1=1152921504606846975=(3*5*7*11)*998200436889045
%e A155747 n=5, m=60, 2^60-1=1152921504606846975=(3*5*7*11*13)*76784648991465
%e A155747 n=6, m=120, 2^120-1=1329227995784915872903807060280344575=
%e A155747 (3*5*7*11*13*17)*5207451355644026063755096120665.
%Y A155747 A002110
%Y A155747 Sequence in context: A000568 A128648 A128646 this_sequence A058254 A076244 
               A058255
%Y A155747 Adjacent sequences: A155744 A155745 A155746 this_sequence A155748 A155749 
               A155750
%K A155747 more,nonn
%O A155747 1,1
%A A155747 Zak Seidov (zakseidov(AT)yahoo.com), Jan 26 2009
%E A155747 a(16)-a(21) from D. S. McNeil (d.mcneil(AT)qmul.ac.uk), Mar 04 2009

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