A332737 Composite terms of A181659, where the sum of the iterated totient function attains a record.

289, 2329, 4369, 4913, 18769, 21331, 35209, 66049, 128881, 197143, 258121, 281929, 516961, 739903, 971203, 1762249, 1942663, 2070721, 2898703, 2952673, 3820819, 4142881, 8288641, 16773619, 16843009, 16974593, 20229241, 21762361, 32472241, 132575071, 187903693

Offset

1,1

Comments

Most of the terms of A181659 are primes. Out of the first 10^4 terms of A181659 only 28 are composites.

The indices of the terms of this sequence in A181659 are 30, 73, 93, 99, 154, 161, 191, 236, 286, 316, ...

The corresponding record values (terms of A126106) are 527, 4223, 8191, 8847, 35527, 39423, 67583, 131327, 246869, 376559, 493739, 550911, 1009981, 1466879, 1884671, 3442687, 3819519, 4089245, 5707263, 5791743, 7444991, 8178491, 16464253, 33260031, 33554431, 33718527, 39989247, 42809067, 63932219, 263382015, 372697723.

Links

Table of n, a(n) for n=1..31.

Mathematica

s[n_] := Plus @@ FixedPointList[EulerPhi, n] - n - 1; seq={}; smax = 1; Do[s1 =s[n];  If[s1 >smax, smax = s1; If[CompositeQ[n], AppendTo[seq, n]]], {n, 1,  5000}]; seq

Crossrefs

Cf. A092693, A126106, A181659.

Sequence in context: A188186 A112077 A152934 * A156575 A296404 A156161

Adjacent sequences: A332734 A332735 A332736 * A332738 A332739 A332740

Keyword

nonn

Author

Amiram Eldar, Feb 21 2020

Status

approved