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URL: https://oeis.org/A245340

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A245340
Smallest m such that A125717(m) = n, or -1 if n never appears.
6
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
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
For RECORDS see A370956 and A370959.
Sequence in context: A230900 A204449 A172393 * A382398 A040174 A084477
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Jul 21 2014
STATUS
approved