A138957 Concatenation of the reversed digits of numbers from 1 to n.

1, 12, 123, 1234, 12345, 123456, 1234567, 12345678, 123456789, 12345678901, 1234567890111, 123456789011121, 12345678901112131, 1234567890111213141, 123456789011121314151, 12345678901112131415161

Offset: 1

Author

Artur Jasinski, Apr 04 2008, Apr 05 2008

Keywords

• nonn
• base

Comments

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

Crossrefs

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

Programs

Mathematica

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
(* or *)
Table[FromDigits[Flatten[Reverse/@IntegerDigits[Range[n]]]],{n,20}] (* Harvey P. Dale, Oct 22 2013 *)