OFFSET
0,1
COMMENTS
a(1)=22 because 2^1 concatenated with 2^1 is 22.
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..200
FORMULA
a(n) = A020338(2^n). - Bruno Berselli, Mar 14 2012
MATHEMATICA
Table[FromDigits[Join[IntegerDigits[2^n], IntegerDigits[2^n]]], {n, 0, 30}] (* Vincenzo Librandi, Mar 14 2012 *)
#*10^IntegerLength[#]+#&/@(2^Range[0, 25]) (* Harvey P. Dale, Aug 29 2024 *)
PROG
(Magma) [Seqint(Intseq(2^n) cat Intseq(2^n)): n in [0..40]]; // Vincenzo Librandi, Mar 14 2012
CROSSREFS
KEYWORD
nonn,easy,base
AUTHOR
Vincenzo Librandi, Jul 10 2010
STATUS
approved