OFFSET
1,2
COMMENTS
RECORDS transform of A009223.
LINKS
Donovan Johnson, Table of n, a(n) for n = 1..500
N. J. A. Sloane, Transforms (The RECORDS transform returns both the high-water marks and the places where they occur).
MATHEMATICA
a[1] = 1; record = 1; a[n_] := a[n] = For[k = a[n-1] + 1, True, k++, g = GCD[DivisorSigma[1, k], EulerPhi[k]]; If[g > record, record = g; Return[k]]]; Table[a[n], {n, 1, 45}] (* Jean-François Alcover, Oct 07 2013 *)
DeleteDuplicates[Table[{k, GCD[DivisorSigma[1, k], EulerPhi[k]]}, {k, 900000}], GreaterEqual[ #1[[2]], #2[[2]]]&][[;; , 1]] (* Harvey P. Dale, Jun 22 2024 *)
PROG
(PARI) mg=0; for(x=1, 1000000, g=A009223(x); if(g>mg, print1(x", "); mg=g))
CROSSREFS
KEYWORD
nonn,nice
AUTHOR
Phil Carmody, Mar 01 2013
STATUS
approved