A222711 Numbers k such that gcd(sigma(k), phi(k)) (A009223) attains record values.

1, 3, 12, 14, 15, 35, 105, 190, 248, 357, 616, 812, 1045, 3080, 3135, 3339, 4064, 5049, 8323, 8636, 10659, 12441, 16065, 19780, 20026, 23374, 24871, 29029, 50065, 58435, 64285, 87685, 124355, 132957, 137885, 140335, 248501, 263055, 317205, 353133, 423657, 596037, 655707, 734517, 894387

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 *)

Prog

(PARI) mg=0; for(x=1, 1000000, g=A009223(x); if(g>mg, print1(x", "); mg=g))

Crossrefs

Cf. A009223, A222712.

Sequence in context: A117061 A341799 A089919 * A176796 A242130 A286386

Adjacent sequences: A222708 A222709 A222710 * A222712 A222713 A222714

Keyword

nonn,nice

Author

Phil Carmody, Mar 01 2013

Status

approved