OFFSET
1,2
COMMENTS
a(n) is the product of the smallest divisors > 1 of all the numbers from 2 to n.
LINKS
Reinhard Zumkeller, Table of n, a(n) for n = 1..1000
EXAMPLE
a(5) = 60. a(6) = 1*2*3*2*5*2 = 120. Also a(6) = a(5) * 2 = 120.
MATHEMATICA
a = {1}; Do[AppendTo[a, a[[n - 1]] FactorInteger[n][[1, 1]]], {n, 2, 25}]; a (* Michael De Vlieger, Aug 25 2015 *)
nxt[{n_, a_}]:={n+1, a*FactorInteger[n+1][[1, 1]]}; NestList[nxt, {1, 1}, 30][[All, 2]] (* Harvey P. Dale, May 03 2018 *)
PROG
(PARI) al(n)=local(v=vector(n)); v[1]=1; for(k=2, n, v[k]=v[k-1]*factor(k)[1, 1]); v \\ Franklin T. Adams-Watters, Jan 13 2012
(PARI) A072486(n)=prod(k=2, n, factor(k)[1, 1]) \\ M. F. Hasler, Jan 13 2012
(Haskell)
a072486 n = a072486_list !! (n-1)
a072486_list = scanl1 (*) a020639_list
-- Reinhard Zumkeller, Apr 10 2014
CROSSREFS
KEYWORD
nonn
AUTHOR
Amarnath Murthy, Jul 13 2002
EXTENSIONS
More terms from Antonio G. Astudillo (afg_astudillo(AT)lycos.com), Apr 25 2003
STATUS
approved