A248024 Lexicographically earliest permutation of the positive integers such that the first digit of a(n+1) divides a(n).

1, 10, 2, 11, 12, 3, 13, 14, 7, 15, 5, 16, 4, 17, 18, 6, 19, 100, 20, 21, 30, 22, 23, 101, 102, 24, 8, 25, 50, 26, 27, 9, 31, 103, 104, 28, 29, 105, 32, 40, 41, 106, 107, 108, 33, 34, 109, 110, 51, 35, 52, 42, 36, 37, 111, 38, 112, 43, 113, 114, 39, 115, 53, 116, 44, 45, 54, 60

Offset

1,2

Links

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

Eric Angelini, Quick and fun permutation, SeqFan list, Sep 29 2014

Index entries for sequences that are permutations of the natural numbers

Mathematica

a[1] = 1; a[n_] := a[n] = Block[{k = 2}, While[Mod[a[n - 1], First@IntegerDigits[k]] != 0 || MemberQ[Array[a, n - 1], k], k++]; k]; Array[a, 68] (* Giorgos Kalogeropoulos, May 12 2023 *)

Prog

(PARI) a(n, S=1, u=2)=for(i=1, n, print1(S", "); for(k=1, 9e9, bittest(u, k)&&next; S%digits(k)[1]&&next; u+=1<<S=k; break)); S
(Haskell)
import Data.List (delete)
a248024 n = a248024_list !! (n-1)
a248024_list = 1 : f 1 [2..] where
  f x zs = g zs where
    g (y:ys) = if x `mod` (a000030 y) == 0
               then y : f y (delete y zs) else g ys
-- Reinhard Zumkeller, Sep 30 2014

Crossrefs

Cf. A248043 (inverse), A000030.

Sequence in context: A323821 A351840 A257277 * A269631 A334737 A334837

Adjacent sequences: A248021 A248022 A248023 * A248025 A248026 A248027

Keyword

nonn,base,look

Author

Eric Angelini and M. F. Hasler, Sep 29 2014

Status

approved