A072488 - OEIS

A072488

a(1) = 1, a(n) = a(n-1) times largest divisor of n <= n^(1/2).

%I #6 Jun 12 2015 11:56:02

%S 1,1,1,2,2,4,4,8,24,48,48,144,144,288,864,3456,3456,10368,10368,41472,

%T 124416,248832,248832,995328,4976640,9953280,29859840,119439360,

%U 119439360,597196800,597196800,2388787200,7166361600,14332723200,71663616000

%N a(1) = 1, a(n) = a(n-1) times largest divisor of n <= n^(1/2).

%t nxt[{n_,a_}]:=Module[{divs=Reverse[Divisors[n+1]]},{n+1,a*SelectFirst[ divs,#<=Sqrt[n+1]&]}]; Transpose[NestList[nxt,{1,1},40]][[2]] (* The program uses the SelectFirst function from Mathematica version 10 *) (* _Harvey P. Dale_, Jun 12 2015 *)

%o (PARI) A033676(n) = {local(d);if(n<2,1,d=divisors(n);d[(length(d)+1)\2])} A072488(n) = if(n<2,1,A033676(n)*A072488(n-1)) a=1;print(a);for(n=2,100,a=a*A033676(n);print(a))

%Y Cf. A072489.

%K nonn

%O 1,4

%A _Amarnath Murthy_, Jul 13 2002

%E PARI program from _Michael B. Porter_, Jan 30 2010