A271504 With a(1) = 1, a(n) is the LCM of all 0 < m < n for which a(m) divides n.

1, 1, 2, 6, 2, 60, 2, 210, 2, 630, 2, 13860, 2, 90090, 2, 90090, 2, 3063060, 2, 29099070, 2, 29099070, 2, 1338557220, 2, 3346393050, 2, 10039179150, 2, 582272390700, 2, 9025222055850, 2, 9025222055850, 2, 18050444111700, 2, 333933216066450, 2, 333933216066450

Offset

1,3

Links

Chai Wah Wu, Table of n, a(n) for n = 1..2309 (n = 1..100 from Peter Kagey)

Formula

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

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

Mathematica

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

Prog

(Python 3.9+)
from math import lcm
from itertools import count, islice
from sympy import divisors
def A271504_gen(): # generator of terms
    A271504_dict = {1:1}
    yield 1
    for n in count(2):
        yield (s:=lcm(*(A271504_dict.get(d, 1) for d in divisors(n, generator=True))))
        A271504_dict[s] = lcm(A271504_dict.get(s, 1), n)
A271504_list = list(islice(A271504_gen(), 40)) # Chai Wah Wu, Nov 17 2022

Crossrefs

Cf. A269347, A271503.

Sequence in context: A122018 A363395 A005729 * A086660 A271503 A102068

Adjacent sequences: A271501 A271502 A271503 * A271505 A271506 A271507

Keyword

nonn

Author

Peter Kagey, Apr 08 2016

Status

approved