A359182 Totient of numbers of least prime signature: a(n) = A000010(A025487(n)).

1, 1, 2, 2, 4, 4, 8, 8, 8, 16, 12, 16, 16, 32, 24, 32, 32, 64, 48, 48, 64, 48, 72, 64, 128, 96, 96, 128, 96, 144, 128, 256, 192, 192, 256, 192, 288, 240, 256, 512, 288, 384, 288, 432, 384, 512, 384, 576, 480, 512, 1024, 576, 768, 480, 576, 864, 768, 1024, 768

Offset

1,3

Comments

This sequence is to A146288 as phi (A000010, the totient function) is to tau (A000005, the number of divisors function).

Links

Vaclav Kotesovec, Table of n, a(n) for n = 1..10000 (terms 1..160 from Hal M. Switkay)

Mathematica

s = {1}; Do[If[GreaterEqual @@ (f = FactorInteger[n])[[;; , 2]] && PrimePi[f[[-1, 1]]] == Length[f], AppendTo[s, EulerPhi[n]]], {n, 2, 3500}]; s (* Amiram Eldar, Dec 19 2022 *)

Prog

(PARI) is(n) = {if(n==1, return(1)); my(f = factor(n));  f[#f~, 1] == prime(#f~) && vecsort(f[, 2], , 4) == f[, 2]}; \\ A025487
lista(nn) = apply(eulerphi, select(is, [1..nn])); \\ Michel Marcus, Dec 19 2022

Crossrefs

Cf. A000005, A000010, A025487, A146288.

Sequence in context: A339820 A287293 A059867 * A046971 A051754 A108747

Adjacent sequences: A359179 A359180 A359181 * A359183 A359184 A359185

Keyword

nonn

Author

Hal M. Switkay, Dec 18 2022

Status

approved