OFFSET
1,3
EXAMPLE
14 is the largest squarefree divisor of a(9) = 28. So a(11) = a(10) + 14 = 57.
MAPLE
with(numtheory): A007947 := proc(n) local i, t1, t2; t1 := ifactors(n)[2]; t2 := mul(t1[i][1], i=1..nops(t1)); end: a:=proc(n) if n=1 or n=2 then 1 else a(n-1)+A007947(a(n-2)) fi end: seq(a(n), n=1..20); # Emeric Deutsch, Jul 24 2006
MATHEMATICA
nxt[{a_, b_}]:={b, b+Max[Select[Divisors[a], SquareFreeQ]]}; Transpose[ NestList[ nxt, {1, 1}, 50]][[1]] (* Harvey P. Dale, Jul 23 2015 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Leroy Quet, Jul 23 2006
EXTENSIONS
More terms from Emeric Deutsch, Jul 24 2006
More terms from R. J. Mathar, May 11 2007
STATUS
approved