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Totient of numbers of least prime signature: a(n) = A000010(A025487(n)).
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%I #17 Mar 25 2023 04:09:21

%S 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,

%T 96,96,128,96,144,128,256,192,192,256,192,288,240,256,512,288,384,288,

%U 432,384,512,384,576,480,512,1024,576,768,480,576,864,768,1024,768

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

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

%H Vaclav Kotesovec, <a href="/A359182/b359182.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..160 from Hal M. Switkay)

%t 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 *)

%o (PARI) is(n) = {if(n==1, return(1)); my(f = factor(n)); f[#f~, 1] == prime(#f~) && vecsort(f[, 2], , 4) == f[, 2]}; \\ A025487

%o lista(nn) = apply(eulerphi, select(is, [1..nn])); \\ _Michel Marcus_, Dec 19 2022

%Y Cf. A000005, A000010, A025487, A146288.

%K nonn

%O 1,3

%A _Hal M. Switkay_, Dec 18 2022