cp's OEIS Frontend

A296078 Least number with the same prime signature as 1+phi(n), where phi = A000010, Euler totient function.

%I A296078 #12 Dec 26 2017 13:45:49
%S A296078 2,2,2,2,2,2,2,2,2,2,2,2,2,2,4,4,2,2,2,4,2,2,2,4,6,2,2,2,2,4,2,2,6,2,
%T A296078 4,2,2,2,4,2,2,2,2,6,4,2,2,2,2,6,6,4,2,2,2,4,2,2,2,2,2,2,2,6,4,6,2,6,
%U A296078 12,4,2,4,2,2,2,2,2,4,2,6,6,2,2,4,6,2,6,2,2,4,2,12,2,2,2,6,2,2,2,2,2,6,2,4,4
%N A296078 Least number with the same prime signature as 1+phi(n), where phi = A000010, Euler totient function.
%H A296078 Antti Karttunen, <a href="/A296078/b296078.txt">Table of n, a(n) for n = 1..65537</a>
%F A296078 a(n) = A046523(A039649(n)) = A046523(1+A000010(n)).
%t A296078 f[n_] := Block[{ps = Last@# & /@ FactorInteger[1 + EulerPhi@n]}, Times @@ ((Prime@ Range@ Length@ ps)^ps)]; Array[f, 105] (* _Robert G. Wilson v_, Dec 11 2017 *)
%o A296078 (PARI)
%o A296078 A046523(n) = { my(f=vecsort(factor(n)[, 2], , 4), p); prod(i=1, #f, (p=nextprime(p+1))^f[i]); }; \\ This function from _Charles R Greathouse IV_, Aug 17 2011
%o A296078 A296078(n) = A046523(1+eulerphi(n));
%Y A296078 Cf. A000010, A046523, A039649, A296079, A296080.
%Y A296078 Cf. A039698 (positions of 2's).
%Y A296078 Cf. also A277906, A296076, A296085, A296092.
%K A296078 nonn
%O A296078 1,1
%A A296078 _Antti Karttunen_, Dec 05 2017