A206527 3^n concatenated with itself.
11, 33, 99, 2727, 8181, 243243, 729729, 21872187, 65616561, 1968319683, 5904959049, 177147177147, 531441531441, 15943231594323, 47829694782969, 1434890714348907, 4304672143046721, 129140163129140163, 387420489387420489
Offset: 0
Examples
a(1)=33 because 3^1 concatenated with 3^1 is 33.
Links
- Vincenzo Librandi, Table of n, a(n) for n = 0..200
Programs
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Magma
[Seqint(Intseq(3^n) cat Intseq(3^n)): n in [0..18]]; // Bruno Berselli, Mar 14 2012
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Mathematica
Table[FromDigits[Join[IntegerDigits[3^n], IntegerDigits[3^n]]], {n, 0, 18}] (* Bruno Berselli, Mar 14 2012 *) Table[3^n 10^IntegerLength[3^n]+3^n,{n,0,20}] (* Harvey P. Dale, May 27 2019 *)
Formula
a(n) = A020338(3^n). - Bruno Berselli, Mar 14 2012