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%I #34 Mar 16 2023 12:14:23
%S 11,33,99,2727,8181,243243,729729,21872187,65616561,1968319683,
%T 5904959049,177147177147,531441531441,15943231594323,47829694782969,
%U 1434890714348907,4304672143046721,129140163129140163,387420489387420489
%N 3^n concatenated with itself.
%H Vincenzo Librandi, <a href="/A206527/b206527.txt">Table of n, a(n) for n = 0..200</a>
%F a(n) = A020338(3^n). - _Bruno Berselli_, Mar 14 2012
%e a(1)=33 because 3^1 concatenated with 3^1 is 33.
%t Table[FromDigits[Join[IntegerDigits[3^n], IntegerDigits[3^n]]], {n, 0, 18}] (* _Bruno Berselli_, Mar 14 2012 *)
%t Table[3^n 10^IntegerLength[3^n]+3^n,{n,0,20}] (* _Harvey P. Dale_, May 27 2019 *)
%o (Magma) [Seqint(Intseq(3^n) cat Intseq(3^n)): n in [0..18]]; // _Bruno Berselli_, Mar 14 2012
%Y Cf. A178664, A000244.
%K nonn,base,easy
%O 0,1
%A _Vincenzo Librandi_, Mar 14 2012