

A222711


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


2



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
(list;
graph;
refs;
listen;
history;
text;
internal format)



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 highwater marks and the places where they occur).


MATHEMATICA

a[1] = 1; record = 1; a[n_] := a[n] = For[k = a[n1] + 1, True, k++, g = GCD[DivisorSigma[1, k], EulerPhi[k]]; If[g > record, record = g; Return[k]]]; Table[a[n], {n, 1, 45}] (* JeanFrançois 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: A063444 A117061 A089919 * A176796 A242130 A286386
Adjacent sequences: A222708 A222709 A222710 * A222712 A222713 A222714


KEYWORD

nonn,nice


AUTHOR

Phil Carmody, Mar 01 2013


STATUS

approved



