# Greetings from The On-Line Encyclopedia of Integer Sequences! http://oeis.org/

Search: id:a055067
Showing 1-1 of 1

%I A055067 #31 Jun 26 2022 02:19:02
%S A055067 1,1,2,3,24,20,720,630,13440,36288,3628800,277200,479001600,444787200,
%T A055067 5811886080,20432412000,20922789888000,1097800704000,6402373705728000,
%U A055067 304112751022080,115852476579840000,2322315553259520000
%N A055067 Product of numbers < n which do not divide n (or 1 if no such numbers exist).
%H A055067 Reinhard Zumkeller, <a href="/A055067/b055067.txt">Table of n, a(n) for n = 1..250</a>
%F A055067 a(n) = A000142(n)/A007955(n).
%e A055067 a(5)=2*3*4=24, a(6)=4*5=20.
%t A055067 Table[Apply[Times, Complement[Range[n], Divisors[n]]], {n, 1, 20}] (* _Geoffrey Critzer_, Dec 13 2014 *)
%t A055067 a[n_] := n!/n^(DivisorSigma[0, n]/2); Array[a, 25] (* _Amiram Eldar_, Jun 26 2022 *)
%o A055067 (Haskell)
%o A055067 a055067 n = product [k | k <- [1..n], mod n k /= 0]
%o A055067 -- _Reinhard Zumkeller_, Feb 06 2012
%o A055067 (PARI) a(n) = n!/vecprod(divisors(n)); \\ _Michel Marcus_, Dec 26 2021
%o A055067 (Python)
%o A055067 from math import factorial, isqrt
%o A055067 from sympy import divisor_count
%o A055067 def A055067(n): return factorial(n)//(isqrt(n)**c if (c:=divisor_count(n)) & 1 else n**(c//2)) # _Chai Wah Wu_, Jun 25 2022
%Y A055067 Cf. A024816.
%Y A055067 Cf. A173540, A072046.
%Y A055067 Cf. A000142, A007955.
%K A055067 easy,nonn
%O A055067 1,3
%A A055067 _Henry Bottomley_, Jun 12 2000
%E A055067 More terms from _David Wasserman_, Mar 15 2002

# Content is available under The OEIS End-User License Agreement: http://oeis.org/LICENSE