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A064916 a(n) = n/lpf(n) + lpf(n) - 1, where lpf = A020639 = least prime factor. 5
2, 3, 3, 5, 4, 7, 5, 5, 6, 11, 7, 13, 8, 7, 9, 17, 10, 19, 11, 9, 12, 23, 13, 9, 14, 11, 15, 29, 16, 31, 17, 13, 18, 11, 19, 37, 20, 15, 21, 41, 22, 43, 23, 17, 24, 47, 25, 13, 26, 19, 27, 53, 28, 15, 29, 21, 30, 59, 31, 61, 32, 23, 33, 17, 34, 67, 35, 25, 36, 71, 37, 73, 38, 27 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,1

COMMENTS

a(n) = A032742(n) + A020639(n) - 1; a(n) <= n and for n > 1 a(n) = n iff n is prime.

LINKS

Harvey P. Dale, Table of n, a(n) for n = 2..1001

EXAMPLE

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

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

MATHEMATICA

lpf[n_]:=Module[{lp=FactorInteger[n][[1, 1]]}, n/lp+lp-1]; Array[lpf, 80, 2] (* Harvey P. Dale, Sep 25 2011 *)

PROG

(PARI) lpf(n)= { local(f); f=factor(n); return(f[1, 1]) } { for (n=2, 1000, L=lpf(n); a=n / L + L - 1; write("b064916.txt", n, " ", a) ) } \\ Harry J. Smith, Sep 28 2009

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

CROSSREFS

Cf. A064920, A064917, A064918, A032742, A020639, A064919.

Sequence in context: A318678 A119674 A064920 * A062854 A057859 A242992

Adjacent sequences:  A064913 A064914 A064915 * A064917 A064918 A064919

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Oct 14 2001

STATUS

approved

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Last modified August 10 06:42 EDT 2020. Contains 336368 sequences. (Running on oeis4.)