OFFSET
1,2
LINKS
Michael De Vlieger, Table of n, a(n) for n = 1..1441
FORMULA
For n >= 2, a(n) = product of the primes <= A073482(n).
EXAMPLE
10 is the 7th squarefree integer. And 2*3*5 = 30 is the smallest primorial number divisible by 10 = 2*5. So a(7) = 30.
MAPLE
issquarefree := proc(n::integer) local nf, ifa, lar ; nf := op(2, ifactors(n)) ; for ifa from 1 to nops(nf) do lar := op(1, op(ifa, nf)) ; if op(2, op(ifa, nf)) >= 2 then RETURN(0) ; fi ; od : RETURN(lar) ; end: primor := proc(n::integer) local resul, nepr ; resul :=2 ; nepr :=3 ; while nepr <= n do resul := resul*nepr ; nepr:=nextprime(nepr) ; od : RETURN(resul) ; end: printf("1, ") ; for n from 2 to 100 do lfa := issquarefree(n) ; if lfa > 0 then printf("%a, ", primor(lfa) ) ; fi ; od : # R. J. Mathar, Apr 02 2006
MATHEMATICA
Select[Array[Which[# == 1, 1, SquareFreeQ@ #, Product[Prime@ i, {i, PrimePi@ FactorInteger[#][[-1, 1]]}], True, 0] &, 50], # > 0 & ] (* Michael De Vlieger, Sep 30 2017 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Leroy Quet, Mar 03 2006
EXTENSIONS
More terms from R. J. Mathar, Apr 02 2006
STATUS
approved