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A032660 a(n) is the smallest positive k such that k concatenated with k + n is a lucky number. 2
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 (list; graph; refs; listen; history; text; internal format)
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-Fran├žois Alcover at A000959 *)

CROSSREFS

Cf. A000959, A032661.

Sequence in context: A104611 A076790 A095693 * A102257 A091425 A205005

Adjacent sequences:  A032657 A032658 A032659 * A032661 A032662 A032663

KEYWORD

nonn,base

AUTHOR

Patrick De Geest, May 15 1998

STATUS

approved

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Last modified September 24 08:44 EDT 2020. Contains 337317 sequences. (Running on oeis4.)