%I #15 Aug 12 2020 12:00:32
%S 1,3,7,15,15,21,15,39,91,555,285,915,3333,1155,1267,2769,4935,10005,
%T 70635,7035,240045,77745,167055,897429,1231635,1066065,1174695
%N a(n) = A143702(n)/2.
%C The product of distinct prime divisors of m*(2^n-m) is also called the radical of that number: rad(m*(2^n-m)).
%t aa = {1}; bb = {1}; rr = {1}; Do[logmax = 0; k = 2^x; w = Floor[(k - 1)/2]; Do[m = FactorInteger[n (k - n)]; rad = 1; Do[rad = rad m[[s]][[1]], {s, 1, Length[m]}]; log = Log[k]/Log[rad]; If[log > logmax, bmin = k - n; amax = n; logmax = log; r = rad], {n, 1, w, 2}]; Print[{x, amax}]; AppendTo[aa, amax]; AppendTo[bb, bmin]; AppendTo[rr, r]; AppendTo[a, {x, logmax}], {x, 2, 15}]; rr (* _Artur Jasinski_ with assistance of _M. F. Hasler_ *)
%Y Cf. A007947, A085152, A085153, A147298-A147307, A147638-A147643.
%K nonn,more
%O 1,2
%A _Artur Jasinski_, Nov 10 2008
%E a(1) added by _Jinyuan Wang_, Aug 11 2020