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%I #10 Aug 05 2023 06:23:21
%S 12,24,84,120,270,672,1488,1638,6200,24384,174592,523776,44736512,
%T 91963648,100651008,459818240,1476304896,10200236032,25769607168,
%U 51001180160,412316073984
%N Admirable numbers that set a new record for largest subtracted divisor.
%C The records set are A000203(a(n))/2 - a(n) = 2, 6, 28, 60, 90, 336, 496, 546, 1240, 8128, 21824,... - _R. J. Mathar_, Feb 12 2008
%t admDiv[n_] := Module[{ab = DivisorSigma[1, n] - 2*n}, If[ab > 0 && EvenQ[ab] && ab/2 < n && Divisible[n, ab/2], ab/2, 0]];
%t seq[nmax_] := Module[{dmax = 0, s = {}, d}, Do[d = admDiv[n]; If[d > dmax, dmax = d; AppendTo[s, n]], {n, 1, nmax}]; s]; seq[6*10^5] (* _Amiram Eldar_, Aug 05 2023 *)
%Y Cf. A000203, A111592, A111646.
%K nonn,more
%O 1,1
%A _Jason Earls_, Aug 10 2005
%E a(13)-a(20) from _Donovan Johnson_, Nov 11 2008
%E a(21) from _Amiram Eldar_, Aug 05 2023