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Least number with identical digits such that the concatenation a(n) a(n-1) ...a(2)a(1) a(2) ... a(n-1) a(n) is a prime.
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%I #7 Dec 05 2013 19:56:37

%S 2,7,3,33,9,77,33,999,1111111,3,33,777777,111111111,77,333333,111,

%T 99999999,3333333333,777777,1,33333333333333333333,

%U 999999999999999999999999999999999999,99999999,999999999999999999999999999999999999999999,3333333333333333333333333

%N Least number with identical digits such that the concatenation a(n) a(n-1) ...a(2)a(1) a(2) ... a(n-1) a(n) is a prime.

%C The resulting primes are given in A090275.

%e 2,727,37273,... etc. are primes.

%Y Cf. A090275.

%K base,nonn

%O 1,1

%A _Amarnath Murthy_, Nov 28 2003

%E More terms from _Sam Alexander_, Jan 06 2005

%E Many further terms from _David Wasserman_, Oct 27 2005