A380414 a(n) = phi(2 + phi(3 + phi(4 + ... + phi(A246655(n))))), where phi is Euler's totient function (A000010).

1, 2, 2, 4, 4, 4, 4, 4, 4, 4, 4, 4, 6, 8, 6, 4, 8, 8, 4, 8, 4, 4, 4, 4, 8, 4, 4, 6, 4, 4, 4, 4, 4, 4, 4, 4, 6, 4, 4, 4, 4, 4, 8, 4, 4, 4, 6, 4, 8, 8, 4, 4, 8, 4, 8, 8, 4, 4, 8, 4, 4, 4, 4, 4, 4, 8, 6, 4, 8, 4, 4, 8, 4, 8, 8, 4, 4, 8, 4, 4, 6, 4, 4, 8, 4, 4, 4, 4, 4, 8

Offset: 1

Author

Paolo Xausa, Jan 24 2025

Keywords

• nonn

Comments

Inspired by A380340, A380341 and A380342.

Conjecture 1: a(n) can be only 1, 2, 4, 6 or 8.

Conjecture 2: for n >= 1110, a(n) = 4.

Links

• Paolo Xausa, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000010, A246655, A380340, A380341, A380342, A380354, A380415.

Programs

Mathematica

With[{pp = Select[Range[1000], PrimePowerQ]}, Table[Fold[EulerPhi[#2 + #] &, 0, pp[[n ;; 1 ;; -1]]], {n, Length[pp]}]]