A138957 - OEIS

%I #8 May 26 2022 09:53:10

%S 1,12,123,1234,12345,123456,1234567,12345678,123456789,12345678901,

%T 1234567890111,123456789011121,12345678901112131,1234567890111213141,

%U 123456789011121314151,12345678901112131415161

%N Concatenation of the reversed digits of numbers from 1 to n.

%C There are no primes in this sequence for n<=7000

%t b = {}; a = {}; Do[w = RealDigits[n]; w = First[w]; Do[AppendTo[a, w[[Length[w] - k + 1]]], {k, 1, Length[w]}]; p = FromDigits[a]; AppendTo[b, p], {n, 1, 21}]; b

%t (* or *)

%t Table[FromDigits[Flatten[Reverse/@IntegerDigits[Range[n]]]],{n,20}] (* _Harvey P. Dale_, Oct 22 2013 *)

%Y Cf. A104759, A000422, A116504, A007908, A116505, A104759, A138789, A138790.

%K nonn,base

%O 1,2

%A _Artur Jasinski_, Apr 04 2008, Apr 05 2008