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A065884 a(n) = A065824(A047845(n+1)).

%I A065884 #11 Aug 12 2024 12:02:42
%S A065884 323,899,1763,5249,3239,979801,5459,10763,9179,9701,10403,12319,
%T A065884 5646547,24569,19109,19043,22499,50819,41309,32639,46979,34579,39059,
%U A065884 125969,49769,49949,154559,48554797,114953,52532203,56624063,195499,75077,79799,72899
%N A065884 a(n) = A065824(A047845(n+1)).
%C A065884 By definition (m+1)*phi(a(n)) = m*sigma(a(n)) where m=A065824(n+1).
%e A065884 A065824(4) = 323, so a(1) = A065824[A047845(1+1)] = 323 A065824(16) = 979801 and a(6) = 979801 = A065824[A047845(1+6)]
%o A065884 (Python)
%o A065884 from math import prod
%o A065884 from itertools import count
%o A065884 from sympy import factorint, primepi
%o A065884 def A065884(n):
%o A065884     m, k = n, primepi(n+1) + n + (n+1>>1)
%o A065884     while m != k:
%o A065884         m, k = k, primepi(k) + n + (k>>1)
%o A065884     m = m-1>>1
%o A065884     for k in count(1):
%o A065884         f = factorint(k)
%o A065884         if (m+1)*k*prod((p-1)**2 for p in f)==m*prod(p**(e+2)-p for p,e in f.items()):
%o A065884             return k # _Chai Wah Wu_, Aug 12 2024
%Y A065884 Cf. A065824, A047845, A000010, A000203.
%K A065884 nonn
%O A065884 1,1
%A A065884 _Labos Elemer_, Nov 27 2001
%E A065884 Name corrected and more terms from _Sean A. Irvine_, Sep 17 2023