|
%I #12 Aug 25 2017 16:40:41
%S 1680,4200,27000,175392,282960,707400,1668480,3344544,5658480,
%T 14146200,48644064,90008880,130110624,225022200,357994728,460763160,
%U 607281696,1926458352,3830537880,5857651296,7840881216,8414628480,8704032876,8843224500,14279194512,29522053080
%N Solutions to 2*x - phi(x) = sigma(x)/2, where phi(x) is the Euler totient function of x.
%D Like A099650 but with totient phi(x) replaced by cototient x - phi(x).
%e phi(1680) = 384, sigma(1680) = 5952 and 2*1680 - 384 = 2976 = 5952/2.
%p with(numtheory): P:=proc(q) local n; for n from 1 to q do
%p if 2*n-phi(n)=sigma(n)/2 then print(n); fi; od; end: P(10^9);
%Y Cf. A000010, A051953, A099650, A111592, A290703.
%K nonn
%O 1,1
%A _Paolo P. Lava_, Aug 09 2017
%E a(10)-a(26) from _Giovanni Resta_, Aug 25 2017
|
