login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 


Least number with the same prime signature as 1+phi(n), where phi = A000010, Euler totient function.
8

%I #12 Dec 26 2017 13:45:49

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

%H Antti Karttunen, <a href="/A296078/b296078.txt">Table of n, a(n) for n = 1..65537</a>

%F a(n) = A046523(A039649(n)) = A046523(1+A000010(n)).

%t 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 (PARI)

%o 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(n) = A046523(1+eulerphi(n));

%Y Cf. A000010, A046523, A039649, A296079, A296080.

%Y Cf. A039698 (positions of 2's).

%Y Cf. also A277906, A296076, A296085, A296092.

%K nonn

%O 1,1

%A _Antti Karttunen_, Dec 05 2017

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified September 20 08:53 EDT 2024. Contains 376067 sequences. (Running on oeis4.)