A258324 Least common multiple of all n - d, where d < n and d is a divisor of n.

1, 1, 2, 6, 4, 60, 6, 84, 24, 360, 10, 3960, 12, 1092, 420, 840, 16, 12240, 18, 13680, 1260, 4620, 22, 1275120, 120, 7800, 936, 19656, 28, 1096200, 30, 52080, 5280, 17952, 7140, 5654880, 36, 25308, 8892, 2489760, 40, 1343160, 42, 397320, 27720

Offset

1,3

Comments

a(n) is a divisor of A072513(n).

a(n) = n-1 if and only if n is prime. - Robert Israel, May 26 2015

Links

Ivan Neretin, Table of n, a(n) for n = 1..1000

Formula

a(n) = lcm(n-d_1, n-d_2, ..., n-d_k) where d_i are the aliquot divisors of n.

Example

a(9) = lcm(9-1, 9-3) = lcm(8, 6) = 24.

Maple

f:= n -> ilcm(seq(n-d, d = numtheory:-divisors(n) minus {n})):
map(f, [$ 1 .. 100]); # Robert Israel, May 26 2015

Mathematica

Table[If[n == 1, 1, LCM @@ (n - Most[Divisors[n]])], {n, 50}]

Prog

(PARI) a(n)=lcm(apply(d->if(d<n, n-d, 1), divisors(n))) \\ Charles R Greathouse IV, May 26 2015
(Haskell)
a258324 n = foldl lcm 1 $ map (n -) $ a027751_row n
-- Reinhard Zumkeller, May 27 2015

Crossrefs

Cf. A072513 (product instead of LCM).

Cf. A027751.

Sequence in context: A264609 A126262 A330078 * A080499 A072513 A022404

Adjacent sequences: A258321 A258322 A258323 * A258325 A258326 A258327

Keyword

nonn

Author

Ivan Neretin, May 26 2015

Status

approved