A245340 Smallest m such that A125717(m) = n, or -1 if n never appears.

0, 1, 4, 2, 8, 21, 3, 5, 18, 16, 14, 12, 10, 6, 1518, 32, 58, 30, 184, 28, 7, 26, 9, 11, 13, 15, 17, 19, 102, 51, 100, 49, 98, 47, 96, 45, 94, 43, 92, 41, 90, 39, 88, 37, 86, 35, 84, 20, 24, 22, 505, 81, 2510, 79, 166, 77, 296, 75, 501, 73, 162, 71, 498, 69

Offset

0,3

Comments

Conjecture: a(n) is never -1.

Links

Reinhard Zumkeller, Table of n, a(n) for n = 0..10000

Ferenc Adorjan, Some characteristics of Leroy Quet's permutation sequences

N. J. A. Sloane, Log-log plot of A370959 vs A370956 (shows terms in A125717 that take the longest to appear).

Prog

(Haskell)
import Data.IntMap (singleton, member, (!), insert)
a245340 n = a245340_list !! n
a245340_list = 0 : f [1..] [1..] 0 (singleton 0 0) where
   f us'@(u:us) vs'@(v:vs) w m
     | u `member` m = (m ! u) : f us vs' w m
     | otherwise    = g (reverse[w-v, w-2*v..1] ++ [w+v, w+2*v..]) where
     g (x:xs) = if x `member` m then g xs else f us' vs x $ insert x v m
(Python)
from itertools import count
def A245340(n):
    a, aset = 0, set()
    for m in count(1):
        if a==n: return m-1
        aset.add(a)
        a = next(a for a in count(a%m, m) if a not in aset) # Chai Wah Wu, Mar 13 2024

Crossrefs

Cf. A245394, A245395, A057167.

For RECORDS see A370956 and A370959.

Sequence in context: A230900 A204449 A172393 * A040174 A084477 A046589

Adjacent sequences: A245337 A245338 A245339 * A245341 A245342 A245343

Keyword

nonn,changed

Author

Reinhard Zumkeller, Jul 21 2014

Status

approved