A166250 a(n) = n-1 plus the largest proper divisor of n.

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, 35, 41, 29, 44, 31, 47, 43, 50, 41, 53, 37, 56, 51, 59, 41, 62, 43, 65, 59, 68, 47, 71, 55, 74, 67, 77, 53, 80, 65, 83, 75, 86, 59, 89, 61, 92, 83, 95, 77, 98, 67, 101, 91, 104, 71, 107

Offset

2,1

Links

G. C. Greubel, Table of n, a(n) for n = 2..10000

Formula

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

Maple

A032742 := proc(n) if n = 1 then 1; else max(op(numtheory[divisors](n) minus {n})) ; fi; end:
A166250 := proc(n) n-1+A032742(n) ; end: seq(A166250(n), n=2..80) ; # R. J. Mathar, Oct 21 2009

Mathematica

f[n_]:=n+Divisors[n+1][[Length[Divisors[n+1]]-1]]; Table[f[n], {n, 2, 6!}] (* Vladimir Joseph Stephan Orlovsky, Mar 03 2010 *)
Table[n+Divisors[n][[-2]]-1, {n, 2, 80}] (* Harvey P. Dale, Jul 21 2015 *)

Prog

(PARI) a(n) = my(d = divisors(n)); n - 1 + d[#d-1]; \\ Michel Marcus, May 08 2016

Crossrefs

Cf. A000027, A032742.

Equals A338281(n)-1.

Sequence in context: A063914 A209187 A357259 * A174088 A304493 A208323

Adjacent sequences: A166247 A166248 A166249 * A166251 A166252 A166253

Keyword

nonn,easy

Author

Juri-Stepan Gerasimov, Oct 10 2009

Extensions

Arbitrarily-defined a(1) removed by R. J. Mathar, Oct 21 2009

Status

approved