A032660 a(n) is the smallest positive k such that k concatenated with k + n is a lucky number.

3, 6, 1, 2, 1, 4, 5, 6, 59, 2, 1, 4, 5, 6, 1, 6, 3, 2, 3, 10, 7, 2, 7, 4, 3, 4, 1, 14, 1, 2, 5, 10, 1, 2, 1, 2, 3, 6, 7, 2, 1, 14, 21, 10, 11, 6, 3, 4, 5, 6, 1, 12, 9, 34, 3, 22, 11, 2, 1, 2, 15, 18, 1, 12, 3, 2, 9, 6, 1, 12, 1, 2, 5, 4, 5, 8, 13, 8, 5, 4, 7, 2, 3, 2, 9, 4, 5, 2, 1, 8, 3, 4, 1, 6, 1

Offset

0,1

Comments

First terms of sequences A032640-A032649, continued with displacements n > 9.

Links

Michael De Vlieger, Table of n, a(n) for n = 0..1000

Example

77th term = 13: 13 + 76 (=77-1) = 89: '13' and '89' = 1389 equals a lucky number.

Mathematica

Block[{L = Array[2 # + 1 &, 10^5 + 1, 0], m, n, r, s}, For[n = 2, n < Length[L], r = L[[n++]]; L = ReplacePart[L, Table[r*i -> Nothing, {i, 1, Length[L]/r}]]]; m = Max[L]; Array[Block[{k = 1}, While[And[# < m, FreeQ[L, #]] &@ Set[s, FromDigits@ Join[IntegerDigits[k], IntegerDigits[k + #]]], k++]; If[s <= m, k, -1]] &, 95, 0]] (* Michael De Vlieger, Jun 24 2020, after Jean-François Alcover at A000959 *)

Crossrefs

Cf. A000959, A032661.

Sequence in context: A076790 A095693 A368569 * A102257 A347196 A091425

Adjacent sequences: A032657 A032658 A032659 * A032661 A032662 A032663

Keyword

nonn,base

Author

Patrick De Geest, May 15 1998

Status

approved