%I #19 Nov 08 2020 23:29:10

%S 2,3,5,5,8,7,11,11,14,11,17,13,20,19,23,17,26,19,29,27,32,23,35,29,38,

%T 35,41,29,44,31,47,43,50,41,53,37,56,51,59,41,62,43,65,59,68,47,71,55,

%U 74,67,77,53,80,65,83,75,86,59,89,61,92,83,95,77,98,67,101,91,104,71,107

%N a(n) = n-1 plus the largest proper divisor of n.

%H G. C. Greubel, <a href="/A166250/b166250.txt">Table of n, a(n) for n = 2..10000</a>

%F a(n) = n - 1 + A032742(n).

%p A032742 := proc(n) if n = 1 then 1; else max(op(numtheory[divisors](n) minus {n})) ; fi; end:

%p A166250 := proc(n) n-1+A032742(n) ; end: seq(A166250(n),n=2..80) ; # _R. J. Mathar_, Oct 21 2009

%t f[n_]:=n+Divisors[n+1][[Length[Divisors[n+1]]-1]];Table[f[n],{n,2,6!}] (* _Vladimir Joseph Stephan Orlovsky_, Mar 03 2010 *)

%t Table[n+Divisors[n][[-2]]-1,{n,2,80}] (* _Harvey P. Dale_, Jul 21 2015 *)

%o (PARI) a(n) = my(d = divisors(n)); n - 1 + d[#d-1]; \\ _Michel Marcus_, May 08 2016

%Y Cf. A000027, A032742.

%Y Equals A338281(n)-1.

%K nonn,easy

%O 2,1

%A _Juri-Stepan Gerasimov_, Oct 10 2009

%E Arbitrarily-defined a(1) removed by _R. J. Mathar_, Oct 21 2009