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a(0) = 1, a(1) = 1; for n > 1, a(n) = lcm( 1, 2, ..., n, a(1)*a(n-1), a(2)*a(n-2), ..., a(n-1)*a(1) ).
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%I #50 Jul 22 2024 19:56:34

%S 1,1,2,6,12,60,360,2520,5040,15120,151200,1663200,9979200,129729600,

%T 1816214400,27243216000,54486432000,926269344000,5557616064000,

%U 105594705216000,1055947052160000,22174888095360000,487847538097920000,11220493376252160000,67322960257512960000

%N a(0) = 1, a(1) = 1; for n > 1, a(n) = lcm( 1, 2, ..., n, a(1)*a(n-1), a(2)*a(n-2), ..., a(n-1)*a(1) ).

%C Squarefree factorials: a(1) = 1, a(n+1) = a(n)* largest squarefree divisor of (n+1). - _Amarnath Murthy_, Nov 28 2004

%C LCM over all partitions of n of the product of the part sizes in the partition. - _Franklin T. Adams-Watters_, May 04 2010

%C a(n) is the product of the lcm of the set of prime factors of k over the range k = 1..n. - _Peter Luschny_, Jun 10 2011

%C a(n) is a divisor of n! and n!/a(n) = A085056(n). - _Robert FERREOL_, Aug 09 2021

%C In consequence of the definition, pseudo-binomial coefficients a(m+n)/(a(m)*a(n)) are natural numbers for all whole numbers m and n, and this is the minimal increasing sequence (for n >= 1) with that property. In consequence of the comment of Adams-Watters, the corresponding pseudo-multinomial coefficients are natural numbers as well. - _Hal M. Switkay_, May 26 2024

%D Paul-Jean Cahen and Jean-Luc Chabert, Integer-valued Polynomials, AMS, Providence, RI, 1997. Math. Rev. 98a:13002. See p. 246.

%H Reinhard Zumkeller, <a href="/A048803/b048803.txt">Table of n, a(n) for n = 0..500</a>

%H Abdelmalek Bedhouche and Bakir Farhi, <a href="https://arxiv.org/abs/2207.07957">On some products taken over the prime numbers</a>, arXiv:2207.07957 [math.NT], 2022. See rho_n p. 3.

%H Bakir Farhi, <a href="https://arxiv.org/abs/1810.07560">On the derivatives of the integer-valued polynomials</a>, arXiv:1810.07560 [math.NT], 2018.

%H <a href="/index/Lc#lcm">Index entries for sequences related to lcm's</a>

%F a(n) = Product_{p prime} p^floor(n/p). See Farhi link p. 16. - _Michel Marcus_, Oct 18 2018

%F For n >=1, a(n) = lcm(1^floor(n/1),2^floor(n/2),...,n^floor(n/n)). - _Robert FERREOL_, Aug 05 2021

%p A048803 := proc(n) local i; mul(ilcm(op(numtheory[factorset](i))), i=1..n) end; seq(A048803(i),i=0..22); # _Peter Luschny_, Jun 10 2011

%p a := n -> mul(NumberTheory:-Radical(i), i=1..n): # _Peter Luschny_, Mar 14 2022

%t a[0] = 1; a[n_] := a[n] = a[n-1] First @ Select[Reverse @ Divisors[n], SquareFreeQ, 1]; Array[a,22,0] (* _Jean-François Alcover_, May 04 2011 *)

%o (PARI) a(n)=local(f); f=n>=0; if(n>1, forprime(p=2,n,f*=p^(n\p))); f

%o (Haskell)

%o a048803 n = a048803_list !! n

%o a048803_list = scanl (*) 1 a007947_list

%o -- _Reinhard Zumkeller_, Jul 01 2013

%o (SageMath)

%o from functools import cache

%o @cache

%o def a_rec(n):

%o if n == 0: return 1

%o return radical(n) * a_rec(n - 1)

%o print([a_rec(n) for n in range(23)]) # _Peter Luschny_, Dec 12 2023

%Y Partial products of A007947.

%K nonn,nice

%O 0,3

%A _Christian G. Bower_, Apr 15 1999

%E Entry improved by comments from _Michael Somos_, Nov 24 2001