A305808 - OEIS

%I #6 Jun 13 2018 23:11:09

%S 1,2,2,5,2,8,2,12,7,12,2,22,2,16,12,28,2,30,2,34,16,24,2,56,11,28,24,

%T 46,2,56,2,64,24,36,16,87,2,40,28,88,2,76,2,70,46,48,2,136,15,70,36,

%U 82,2,108,24,120,40,60,2,172,2,64,62,144,28,116,2,106,48,108,2,228,2,76,70,118,24,136,2,216,81,84,2,236,36,88,60,184,2,228,28

%N Dirichlet convolution of A032742 (the largest proper divisor of n) with itself.

%H Antti Karttunen, <a href="/A305808/b305808.txt">Table of n, a(n) for n = 1..65537</a>

%F a(n) = Sum_{d|n} A032742(n/d)*A032742(d).

%o (PARI)

%o A032742(n) = if(1==n,n,n/vecmin(factor(n)[,1]));

%o A305808(n) = sumdiv(n,d,A032742(n/d)*A032742(d));

%Y Cf. A032742, A300236, A300239, A305807.

%K nonn

%O 1,2

%A _Antti Karttunen_, Jun 13 2018