|
%I #10 Aug 22 2017 10:37:46
%S 9504,16560,41400,5048568,10889856,11941344,16255080,131473152,
%T 5517818880,107561120688,612014161920
%N Numbers n such that psi(n) is the sum of proper divisors of n where psi(n) = A001615(n).
%C Or numbers n such that sigma(n) = psi(n) + n where psi(n) = A001615(n) and sigma(n) = A000203(n).
%C 9504 = 2^5*3^3*11 is the smallest number with this property.
%e 16560 is a term because sigma(16560) = 58032 and psi(16560) = 41472; sigma(16560) - psi(16560) = 16560.
%o (PARI) a001615(n) = n*sumdivmult(n, d, issquarefree(d)/d);
%o isok(n) = sigma(n)==a001615(n)+n; \\ after _Charles R Greathouse IV_ at A001615
%Y Cf. A000203, A001065, A001615.
%K nonn,more
%O 1,1
%A _Altug Alkan_, Aug 21 2017
%E a(9)-a(11) from _Giovanni Resta_, Aug 21 2017
| 