OFFSET
2,2
LINKS
Max Alekseyev, Table of n, a(n) for n = 2..145 (terms for n = 2..74 from Amiram Eldar)
Reinhard Zumkeller, Products of largest prime factors of numbers <= n
MAPLE
A000142 := proc(n) RETURN(n!) ; end: A006530 := proc(n) local i, t1, t2, t3, t4; if n = 1 then RETURN(1) ; else t1 := numtheory[divisors](n); t2 := convert(t1, list); t3 := sort(t2); t4 := nops(t3); for i from 1 to t4 do if isprime(t3[t4+1-i]) then RETURN(t3[t4+1-i]); fi; od; RETURN(1); fi ; end: A104350 := proc(n) local k, resul ; resul := 1 ; for k from 1 to n do resul := resul*A006530(k) ; od ; RETURN(resul) ; end: A104357 := proc(n) A104350(n)-1 ; end: A104362 := proc(n) numtheory[sigma](A104357(n)) ; end: for n from 2 to 30 do printf("%d, ", A104362(n)) ; od ; # R. J. Mathar, Oct 30 2006
MATHEMATICA
a[n_] := DivisorSigma[1, Product[FactorInteger[k][[-1, 1]], {k, 1, n}]-1]; Table[a[n], {n, 2, 23}] (* Jean-François Alcover, Feb 10 2018 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Mar 06 2005
EXTENSIONS
Corrected and extended by R. J. Mathar, Oct 30 2006
STATUS
approved