The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A340727

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A340727

a(n) is the smallest integer that can be written as a product of n distinct integers > 1 in at least two different ways.
(history; published version)

#16 by Peter Luschny at Mon Jan 18 18:05:17 EST 2021

STATUS

editing

approved

#15 by Peter Luschny at Mon Jan 18 18:04:49 EST 2021

EXTENSIONS

More terms from James Rayman, Jan 18 2021

STATUS

reviewed

editing

Discussion

Mon Jan 18

18:05

Peter Luschny: No need for extension line.

#14 by Michel Marcus at Mon Jan 18 16:59:05 EST 2021

STATUS

proposed

reviewed

#13 by James Rayman at Mon Jan 18 16:11:35 EST 2021

STATUS

editing

proposed

#12 by James Rayman at Mon Jan 18 16:11:00 EST 2021

LINKS

James Rayman, <a href="/A340727/b340727.txt">Table of n, a(n) for n = 2..400</a>

EXTENSIONS

More terms from James Rayman, Jan 18 2021

STATUS

approved

editing

#11 by Michel Marcus at Mon Jan 18 03:53:56 EST 2021

STATUS

reviewed

approved

#10 by Joerg Arndt at Mon Jan 18 03:07:19 EST 2021

STATUS

proposed

reviewed

#9 by James Rayman at Mon Jan 18 02:08:38 EST 2021

STATUS

editing

proposed

#8 by James Rayman at Mon Jan 18 02:07:41 EST 2021

PROG

(Python)

from heapq import *

import math

def a(n):

prev, visited, v = 0, set(), list(range(2, n+2))

pq = [(math.factorial(n+1), v)]

while True:

prod, v = heappop(pq)

if tuple(v) in visited: continue

visited.add(tuple(v))

if prev != prod: prev = prod

else: return prod

for i in range(n):

if i == n-1 or v[i] + 1 < v[i+1]:

u = v[:]

u[i] += 1

heappush(pq, (prod // v[i] * u[i], u))

STATUS

proposed

editing

#7 by James Rayman at Mon Jan 18 00:19:09 EST 2021

STATUS

editing

proposed

Discussion

Mon Jan 18

00:58

Michel Marcus: can you add a program