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A064920 a(n) = n/gpf(n) + gpf(n) - 1, where gpf = A006530 = greatest prime factor. 6
2, 3, 3, 5, 4, 7, 5, 5, 6, 11, 6, 13, 8, 7, 9, 17, 8, 19, 8, 9, 12, 23, 10, 9, 14, 11, 10, 29, 10, 31, 17, 13, 18, 11, 14, 37, 20, 15, 12, 41, 12, 43, 14, 13, 24, 47, 18, 13, 14, 19, 16, 53, 20, 15, 14, 21, 30, 59, 16, 61, 32, 15, 33, 17, 16, 67, 20, 25, 16, 71, 26, 73, 38, 19, 22 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,1

COMMENTS

a(n) = A052126(n) + A006530(n) - 1; a(n) <= n and for n > 1: a(n) = n iff n is prime.

LINKS

Harry J. Smith, Table of n, a(n) for n = 2..1000

EXAMPLE

a(18) = 18/2 + 2 - 1 = 10;

a(19) = 19/19 + 19 - 1 = 19.

MATHEMATICA

a[n_] := (g = FactorInteger[n][[-1, 1]]; n/g + g - 1); a /@ Range[2, 76] (* Jean-Fran├žois Alcover, Apr 06 2011 *)

PROG

(PARI) gpf(n)= { local(f); f=factor(n)~; return(f[1, length(f)]) } { for (n=2, 1000, g=gpf(n); a=n / g + g - 1; write("b064920.txt", n, " ", a) ) } \\ Harry J. Smith, Sep 29 2009

(PARI) a(n) = my(p = vecmax(factor(n)[, 1])); n/p + p - 1; \\ Michel Marcus, Jun 19 2018

CROSSREFS

Cf. A064916, A064921, A064922, A006530, A052126, A064923, A064924.

Sequence in context: A296075 A318678 A119674 * A064916 A062854 A057859

Adjacent sequences:  A064917 A064918 A064919 * A064921 A064922 A064923

KEYWORD

nice,nonn

AUTHOR

Reinhard Zumkeller, Oct 14 2001

STATUS

approved

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Last modified August 13 08:27 EDT 2020. Contains 336442 sequences. (Running on oeis4.)