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A378058
Numbers k that divide A378056(k) = gcd(lcm{d+1 : d|k}, lcm{d-1 : d > 1 and d|k}).
3
1, 60, 210, 360, 420, 504, 630, 660, 840, 924, 1092, 1260, 1320, 1560, 1848, 1980, 2184, 2310, 2520, 2640, 2772, 3080, 3120, 3276, 3465, 3960, 4080, 4284, 4620, 4680, 5320, 5460, 5544, 6006, 6552, 6732, 6840, 6864, 6930, 7140, 7800, 7854, 7920, 8190, 8280, 8568, 8580, 9240, 9360, 9828
OFFSET
1,2
COMMENTS
After the first term a(1) = 1, the next odd term is a(25) = 3465, the next term that is coprime to 6 is a(308) = 95095, and the next term that is coprime to 30 is a(13544) = 10023013.
LINKS
EXAMPLE
60 is a term since A378056(60) = 4620 = 60 * 77 is divisible by 60.
MATHEMATICA
s[n_] := Module[{d = Divisors[n]}, GCD[LCM @@ (d + 1), LCM @@ (Rest @ d - 1)]]; s[1] = 1; Select[Range[10000], Divisible[s[#], #] &]
PROG
(PARI) is(k) = {my(d = divisors(k)); !(lcm(apply(x->x+1, d)) % k) && !(lcm(apply(x -> if(x > 1, x-1, x), d)) % k); }
CROSSREFS
Intersection of A377950 and A377952.
A378059 is a subsequence.
Sequence in context: A292223 A112827 A181333 * A380302 A082529 A126248
KEYWORD
nonn
AUTHOR
Amiram Eldar, Nov 15 2024
STATUS
approved