%I #8 Sep 08 2022 08:46:01
%S 11,77,4949,343343,24012401,1680716807,117649117649,823543823543,
%T 57648015764801,4035360740353607,282475249282475249,
%U 19773267431977326743,1384128720113841287201,9688901040796889010407,678223072849678223072849
%N 7^n concatenated with itself.
%H Vincenzo Librandi, <a href="/A206529/b206529.txt">Table of n, a(n) for n = 0..200</a>
%F a(n) = A020338(7^n).
%e a(1)=77 because 7^1 concatenated with 7^1 is 77.
%t Table[FromDigits[Join[IntegerDigits[7^n],IntegerDigits[7^n]]],{n,0,20}]
%t #*10^IntegerLength[#]+#&/@(7^Range[0,20]) (* _Harvey P. Dale_, Jul 19 2022 *)
%o (Magma) [Seqint(Intseq(7^n) cat Intseq(7^n)): n in [0..20]];
%Y Cf. A000420, A000351, A178664, A206527, A206528.
%K nonn,base,easy
%O 0,1
%A _Vincenzo Librandi_, Mar 18 2012