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A166250 a(n) = n-1 plus the largest proper divisor of n. 2
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 (list; graph; refs; listen; history; text; internal format)
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: A267453 A063914 A209187 * 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

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Last modified July 24 06:56 EDT 2021. Contains 346273 sequences. (Running on oeis4.)