A077292 Numbers k with the property that k divides one of the concatenations (k-1)(k-2) or (k-2)(k-1).

2, 3, 4, 6, 7, 17, 34, 51, 67, 167, 334, 501, 667, 1667, 3334, 5001, 6667, 14286, 16667, 33334, 50001, 66667, 166667, 333334, 500001, 666667, 1666667, 2857143, 3333334, 5000001, 6666667, 16666667, 33333334, 50000001, 66666667, 1052631579, 1666666667, 3333333334, 5000000001, 6666666667

Offset

1,1

Links

Table of n, a(n) for n=1..40.

Example

6 and 7 are terms: 6 divides 54, 7 divides 56.

Mathematica

c[r_, s_] := ToExpression[ToString[r] <> ToString[s]]; Do[k = c[n-1, n-2]; m = c[n-2, n-1]; If[Mod[k, n] == 0 || Mod[m, n] == 0, Print[n]], {n, 2, 10^8}] (* Ryan Propper, Oct 11 2005 *)
ccQ[n_]:=Module[{id1=IntegerDigits[n-1], id2=IntegerDigits[n-2]}, Divisible[ FromDigits[ Join[id1, id2]], n]||Divisible[FromDigits[Join[id2, id1]], n]]; Select[Range[2, 67000000], ccQ] (* Harvey P. Dale, Jun 18 2012 *)

Crossrefs

Sequence in context: A162570 A073639 A130776 * A270475 A171249 A036413

Adjacent sequences: A077289 A077290 A077291 * A077293 A077294 A077295

Keyword

base,nonn

Author

Amarnath Murthy, Nov 03 2002

Extensions

More terms from Ray G. Opao, Sep 28 2005

a(34)-a(35) from Ryan Propper, Oct 11 2005

a(36)-a(40) from Sean A. Irvine, May 14 2025

Status

approved