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A015702 Numbers n where phi(n) + sigma(n) increases. 6
1, 2, 3, 4, 5, 6, 8, 10, 12, 16, 18, 20, 24, 30, 36, 40, 42, 48, 56, 60, 72, 84, 90, 96, 108, 120, 144, 168, 180, 210, 216, 240, 280, 288, 300, 324, 336, 360, 420, 480, 504, 540, 576, 600, 648, 660, 672, 720, 840, 960, 1008, 1080, 1200, 1260, 1440 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Donovan Johnson, Table of n, a(n) for n = 1..1288 (terms < 10^12)

Richard K. Guy, Divisors and desires, Amer. Math. Monthly, 104 (1997), 359-360.

MATHEMATICA

seq = {}; sm = 0; s = 0; Do[s = EulerPhi[n] + DivisorSigma[1, n];

If[s > sm, sm = s; AppendTo[seq, n]], {n, 1, 1500}]; seq (* Amiram Eldar, Dec 05 2018 *)

PROG

(PARI) f(n)=eulerphi(n=factor(n))+sigma(n)

r=0; for(n=1, 1e6, t=f(n); if(t>r, r=t; print1(n", "))) \\ Charles R Greathouse IV, Nov 27 2013

CROSSREFS

Cf. A000203, A000010, A018892, A018894, A065387.

Sequence in context: A279077 A018541 A018293 * A245709 A253789 A029747

Adjacent sequences: A015699 A015700 A015701 * A015703 A015704 A015705

KEYWORD

nonn

AUTHOR

Robert G. Wilson v

STATUS

approved

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Last modified December 5 15:27 EST 2022. Contains 358588 sequences. (Running on oeis4.)