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%I #11 Apr 19 2018 12:36:09
%S 33,77,31,17,81,11,57,27,21,61,17,17,61,57,17,17,41,21,11,27,41,31,21,
%T 41,41,41,81,57,57,51,77,17,11,47,81,61,11,41,91,17,27,17,31,11,27,11,
%U 31
%N Concatenation of initial and final digit of n-th Mersenne prime A000668(n).
%F a(n) = A073729(A000668(n)). - _Michel Marcus_, Apr 17 2018
%e a(5)=81 because the 5th Mersenne prime is 8191, A000668(5)=8191.
%Y Cf. A000668, A073729, A080172, A135613, A138840, A138842, A138843.
%K base,nonn,more,less
%O 1,1
%A _Omar E. Pol_, Apr 01 2008
%E a(40)-a(47) from _Ivan Panchenko_, Apr 17 2018