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

1,2

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

Mathematica

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

Crossrefs

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

Sequence in context: A071805 A063511 A334789 * A283207 A164717 A164715

Adjacent sequences: A380411 A380412 A380413 * A380415 A380416 A380417

Keyword

nonn

Author

Paolo Xausa, Jan 24 2025

Status

approved