A271504 - OEIS

%I #18 Nov 18 2022 08:32:05

%S 1,1,2,6,2,60,2,210,2,630,2,13860,2,90090,2,90090,2,3063060,2,

%T 29099070,2,29099070,2,1338557220,2,3346393050,2,10039179150,2,

%U 582272390700,2,9025222055850,2,9025222055850,2,18050444111700,2,333933216066450,2,333933216066450

%N With a(1) = 1, a(n) is the LCM of all 0 < m < n for which a(m) divides n.

%H Chai Wah Wu, <a href="/A271504/b271504.txt">Table of n, a(n) for n = 1..2309</a> (n = 1..100 from Peter Kagey)

%F a(2n + 1) = 2 for all n > 1.

%F a(n) is even for all n > 2.

%t a = {1}; Do[AppendTo[a, LCM @@ Select[Range[n - 1], Divisible[n, a[[#]]] &]], {n, 2, 40}]; a (* _Michael De Vlieger_, Apr 08 2016 *)

%o (Python 3.9+)

%o from math import lcm

%o from itertools import count, islice

%o from sympy import divisors

%o def A271504_gen(): # generator of terms

%o     A271504_dict = {1:1}

%o     yield 1

%o     for n in count(2):

%o         yield (s:=lcm(*(A271504_dict.get(d,1) for d in divisors(n,generator=True))))

%o         A271504_dict[s] = lcm(A271504_dict.get(s,1),n)

%o A271504_list = list(islice(A271504_gen(),40)) # _Chai Wah Wu_, Nov 17 2022

%Y Cf. A269347, A271503.

%K nonn

%O 1,3

%A _Peter Kagey_, Apr 08 2016