A138793 a(n) = concatenation of reversed digits of natural numbers from n down to 1.

1, 21, 321, 4321, 54321, 654321, 7654321, 87654321, 987654321, 1987654321, 1101987654321, 211101987654321, 31211101987654321, 4131211101987654321, 514131211101987654321, 61514131211101987654321, 7161514131211101987654321

Offset

1,2

Comments

Note that leading zeros are not omitted when writing down digits in reversed order. So 10 reversed becomes 01. - N. J. A. Sloane, Jan 23 2017

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..100

Maple

read(transforms): A138793 := proc(n) return digrev(parse(cat($(1..n)))): end: seq(A138793(n), n=1..17); # Nathaniel Johnston, Jun 26 2011

Mathematica

b = {}; a = {}; Do[w = RealDigits[n]; w = First[w]; Do[AppendTo[a, w[[k]]], {k, 1, Length[w]}]; p = FromDigits[Reverse[a]]; AppendTo[b, p], {n, 1, 61}]; b (* Artur Jasinski, Mar 30 2008 *)
lst = {}; Table[FromDigits[Reverse[lst = Join[lst, IntegerDigits[n]]]], {n, 1, 15}] (* Robert Price, Mar 22 2015 *)

Prog

(Magma) [Seqint(&cat[Reverse(Intseq(k)): k in [1..n]]): n in [1..16]]; // Bruno Berselli, May 27 2011
(PARI) a(n) = my(s = ""); forstep (k=n, 1, -1, sk = digits(k); forstep (j=#sk, 1, -1, s = concat(s, sk[j]))); eval(s); \\ Michel Marcus, Jan 28 2017

Crossrefs

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

Sequence in context: A260487 A057138 A104759 * A014925 A000422 A060554

Adjacent sequences: A138790 A138791 A138792 * A138794 A138795 A138796

Keyword

nonn,easy,base

Author

Artur Jasinski, Mar 30 2008, Apr 04 2008

Status

approved