A079700 - OEIS

%I #16 Aug 23 2024 09:05:38

%S 1,1,1,1,1,1,2,1,2,1,1,1,1,1,1,1,2,1,1,1,3,1,1,1,1,1,1,2,1,1,1,1,1,1,

%T 1,2,1,2,1,3,1,1,1,1,1,2,1,1,1,1,4,2,1,1,1,1,1,1,2,1,1,1,2,1,1,3,1,1,

%U 1,1,1,2,1,1,2,1,1,1,2,1,2,1,1,1,1,1,3,1,1,2,3,1,4

%N a(n) is the 2-adic valuation of the n-th even nontotient.

%H Charles R Greathouse IV, <a href="/A079700/b079700.txt">Table of n, a(n) for n = 1..10000</a>

%H Maxim Rytin, <a href="http://library.wolfram.com/infocenter/MathSource/696/">Finding the Inverse of Euler Totient Function</a> (1999).

%F a(n) = A007814(A005277(n)). - _Michel Marcus_, Jul 01 2017

%e A005277(10)=86, therefore a(10)=1.

%t IntegerExponent[Select[Range[2, 500, 2], invphi[#] == {}&], 2] (* _Jean-François Alcover_, Jul 01 2017, using Maxim Rytin's invphi function *)

%o (PARI) lista(nn)=forstep(n=2, nn, 2, if (!istotient(n), print1(valuation(n, 2), ", "));); \\ _Michel Marcus_, Jul 01 2017

%Y Cf. A005277, A007814.

%K nonn

%O 1,7

%A _Jon Perry_, Jan 31 2003

%E More terms from _Jean-François Alcover_, Jul 01 2017

%E Offset corrected by _Charles R Greathouse IV_, Jul 02 2017