A113595 Least multiple of n which is greater than n and is a concatenation of two successive natural numbers k and k+1.

12, 12, 12, 12, 45, 12, 56, 56, 45, 910, 1617, 1920, 78, 56, 45, 1920, 34, 1314, 2223, 1920, 1617, 2728, 2829, 1920, 2425, 78, 3132, 56, 3132, 1920, 2728, 1920, 1617, 3536, 910, 3132, 2627, 4142, 78, 1920, 2829, 3738, 2021, 2728, 4950, 5152, 2021, 1920, 1617

Offset

1,1

Comments

'Multiple' means >1 and the concatenation is left-to-right only.

Links

Paul Tek, Table of n, a(n) for n = 1..10000

Mathematica

Module[{nn=99, cc, t}, cc=Table[FromDigits[Flatten[Join[ IntegerDigits/@ {n, n+1}]]], {n, nn}]; Table[t=Select[cc, Divisible[#, x]&]; If[t[[1]]>x, t[[1]], t[[2]]], {x, 50}]] (* Harvey P. Dale, Sep 17 2020 *)

Prog

(Python)
def a(n):
    k, concat = 1, 12
    while concat <= n or concat%n:
        k += 1
        concat = int(str(k)+str(k+1))
    return concat
print([a(n) for n in range(1, 50)]) # Michael S. Branicky, Dec 12 2021

Crossrefs

Cf. A111381.

Sequence in context: A302341 A064162 A028996 * A109053 A186100 A334245

Adjacent sequences: A113592 A113593 A113594 * A113596 A113597 A113598

Keyword

base,nonn

Author

Amarnath Murthy, Nov 07 2005

Extensions

Corrected and extended by Hans Havermann, Nov 08 2005

Definition clarified by Harvey P. Dale, Sep 17 2020

Status

approved