A065392 a(n) = A062401(A065391(n)): phi(sigma(m)) peak values for numbers m (listed in A065391) at which those peaks are first reached.

1, 2, 6, 8, 12, 30, 36, 72, 126, 180, 360, 432, 660, 930, 1512, 2160, 3300, 3780, 5184, 6552, 11160, 13860, 19800, 23232, 32760, 45360, 47520, 50400, 58080, 61776, 102300, 110160, 137592, 155520, 163296, 196560, 212960, 252000, 272160, 284580

Offset: 1

Author

Labos Elemer, Nov 14 2001

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..249 (terms 1..100 from Harry J. Smith)

Crossrefs

Cf. A000010, A000203, A062401, A065389, A065390, A065391, A065393, A065394.

Programs

Mathematica

With[{s = Array[EulerPhi@ DivisorSigma[1, #] &, 10^5]}, Union@ FoldList[Max, s] ] (* Michael De Vlieger, Dec 06 2018 *)

PARI

{ n=r=0; for (m=1, 10^9, x=eulerphi(sigma(m)); if (x > r, r=x; write("b065392.txt", n++, " ", x); if (n==100, return)) ) } \\ Harry J. Smith, Oct 18 2009