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A248025 Lexicographically earliest permutation of the positive integers such that the first digit of a(n+1) is the digital root of a(n). 4
1, 10, 11, 2, 20, 21, 3, 30, 31, 4, 40, 41, 5, 50, 51, 6, 60, 61, 7, 70, 71, 8, 80, 81, 9, 90, 91, 12, 32, 52, 72, 92, 22, 42, 62, 82, 13, 43, 73, 14, 53, 83, 23, 54, 93, 33, 63, 94, 44, 84, 34, 74, 24, 64, 15, 65, 25, 75, 35, 85, 45, 95, 55, 16, 76, 46, 17, 86, 56, 26, 87, 66, 36, 96 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

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

E. Angelini, Fun and quick permutation (with a digital root), SeqFan list, Sep 29 2014

Index entries for sequences that are permutations of the natural numbers

PROG

(PARI) a(n, S=1, u=2)={for(i=1, n, print1(S", "); S=(S-1)%9+1; for(k=1, 9e9, bittest(u, k)&&next; S==digits(k)[1]||next; u+=1<<S=k; break)); S}

(Haskell)

import Data.List (delete)

a248025 n = a248025_list !! (n-1)

a248025_list = 1 : f 1 [2..] where

  f x zs = g zs where

    g (y:ys) = if a000030 y == a010888 x

               then y : f y (delete y zs) else g ys

-- Reinhard Zumkeller, Sep 30 2014

CROSSREFS

Cf. A010888 (digital root); similar sequences: A248024,...

Cf. A247879 (inverse), A000030.

Sequence in context: A328752 A173821 A101807 * A303501 A289985 A065517

Adjacent sequences:  A248022 A248023 A248024 * A248026 A248027 A248028

KEYWORD

nonn,base

AUTHOR

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

STATUS

approved

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Last modified August 9 13:57 EDT 2020. Contains 336323 sequences. (Running on oeis4.)