A206529 7^n concatenated with itself.
11, 77, 4949, 343343, 24012401, 1680716807, 117649117649, 823543823543, 57648015764801, 4035360740353607, 282475249282475249, 19773267431977326743, 1384128720113841287201, 9688901040796889010407, 678223072849678223072849
Offset: 0
Examples
a(1)=77 because 7^1 concatenated with 7^1 is 77.
Links
- Vincenzo Librandi, Table of n, a(n) for n = 0..200
Programs
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Magma
[Seqint(Intseq(7^n) cat Intseq(7^n)): n in [0..20]];
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Mathematica
Table[FromDigits[Join[IntegerDigits[7^n],IntegerDigits[7^n]]],{n,0,20}] #*10^IntegerLength[#]+#&/@(7^Range[0,20]) (* Harvey P. Dale, Jul 19 2022 *)
Formula
a(n) = A020338(7^n).