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A328175 a(n) is the largest integer k such that sigma(k)/(d(k)*sopf(k)) = n where d=A000005, sigma=A000203 and sopf=A008472.

%I A328175 #14 Oct 20 2019 10:31:51
%S A328175 42,470,923,2159,12924,3735,4316,8786,23939,24412,76502,26768,28612,
%T A328175 47849,145620,36002,118204,189143,116999,105657,109559,252474,142687,
%U A328175 236860,504899,265682,388798,1558808,154559,345687,709564,544829,383086,652049,361905,1193075
%N A328175 a(n) is the largest integer k such that sigma(k)/(d(k)*sopf(k)) = n where d=A000005, sigma=A000203 and sopf=A008472.
%o A328175 (PARI) sopf(f) = sum(j=1, #f~, f[j, 1]); \\ A008472
%o A328175 lista(nn) = {/* nn should be > 10^7 */ my(nmax = 43, v = vector(nmax, k, List())); for (n=2, nn, my(f=factor(n), q); if (denominator(q=sigma(f)/(numdiv(f)*sopf(f))) == 1, if (q <= nmax, listput(v[q], n)););); for (i=1, nmax, if (#v[i] == 0, break); print1(vecmax(Vec(v[i])), ", "););}
%Y A328175 Cf. A000005, A000203, A008472, A134382, A328051, A328052, A328174.
%K A328175 nonn
%O A328175 1,1
%A A328175 _Michel Marcus_, Oct 06 2019