A015702 Numbers n where phi(n) + sigma(n) increases.

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

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 *)
DeleteDuplicates[Table[{n, EulerPhi[n]+DivisorSigma[1, n]}, {n, 1500}], GreaterEqual[ #1[[2]], #2[[2]]]&][[;; , 1]] (* Harvey P. Dale, Mar 13 2023 *)

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: A361785 A361319 A018293 * A362127 A364960 A245709

Adjacent sequences: A015699 A015700 A015701 * A015703 A015704 A015705

Keyword

nonn

Author

Robert G. Wilson v

Status

approved