A393976 a(n) = phi(n)^2 + phi(n) + 1, where phi is Euler's totient function.

3, 3, 7, 7, 21, 7, 43, 21, 43, 21, 111, 21, 157, 43, 73, 73, 273, 43, 343, 73, 157, 111, 507, 73, 421, 157, 343, 157, 813, 73, 931, 273, 421, 273, 601, 157, 1333, 343, 601, 273, 1641, 157, 1807, 421, 601, 507, 2163, 273, 1807, 421, 1057, 601, 2757, 343, 1641, 601, 1333, 813, 3423

Offset

1,1

Links

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

Index entries for sequences related to totient function phi(n).

Formula

a(n) = A127473(n) + A000010(n) + 1.

Mathematica

A393976[n_] := #^2 + # + 1 & [EulerPhi[n]]; Array[A393976, 100]

Prog

(PARI) a(n) = my(t=eulerphi(n)); t^2+t+1; \\ Michel Marcus, Mar 05 2026

Crossrefs

Cf. A000010, A117308, A127473.

Sequence in context: A147236 A146599 A107222 * A050613 A145940 A147103

Adjacent sequences: A393973 A393974 A393975 * A393977 A393978 A393979

Keyword

nonn,easy

Author

Paolo Xausa, Mar 05 2026

Status

approved