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 A370956 vs A370959 (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
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Jul 21 2014
STATUS
approved