Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #14 Aug 28 2019 10:25:29
%S 3,14,488,16072,284229,29221621,25014312576
%N a(n) = least k such that GCD of sigma(k) = A000203(k) and phi(k) = A000010(k) equals n-th primorial = A002110(n).
%C a(8) <= 1524139588224. - _Donovan Johnson_, Dec 14 2009
%F a(n) = Min_{k : A081396(k) = A002110(n)}.
%e k=284229: sigma(284229) = 482790 = 2*3*5*7*11*19, phi(284229) = 166320 = 2*2*2*3*3*3*3*5*7*11, common factor set = {2,3,5,7,11}, gcd(sigma,phi) = 2310.
%Y Cf. A000010, A000203, A002110, A081383, A081396.
%K nonn,more
%O 1,1
%A _Labos Elemer_, Mar 28 2003
%E a(6) corrected and a(7) from _Donovan Johnson_, Dec 14 2009