This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A351448 #21 Apr 21 2023 06:29:53
%S A351448 8181,400869,1507005,3918213,11151837,22002273,26669007,47319957,
%T A351448 58170393,73843245,75825981,83488077,94338513,108277641,119656197,
%U A351448 126889821,137740257,163057941,184758813,191992437,199226061,202842873,204768225,220926933,228160557,258457473,264328677,277602471,300496797
%N A351448 Odd numbers k for which A003958(sigma(k)) = 2*A003958(k), where A003958 is multiplicative with a(p^e) = (p-1)^e and sigma is the sum of divisors function.
%C A351448 Odd numbers k such that A351442(k) = 2*A003958(k).
%C A351448 Any hypothetical odd term of A005820, if such a term exists, should appear in this sequence, in A347391, and in A016754 (odd squares).
%C A351448 None of the first 33 terms is a square, and all of them except 75825981 and 204768225 are multiples of 81. Note that 81 is one of the terms of A008848 (and of A231484), squares whose sum of divisors is also square (with A000203(81) = 121).
%H A351448 <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a>
%o A351448 (PARI)
%o A351448 A003958(n) = { my(f = factor(n)); for(i=1, #f~, f[i, 1]--); factorback(f); };
%o A351448 isA351448(n) = (n%2 && (A003958(sigma(n)) == 2*A003958(n)));
%Y A351448 Odd terms in A351447.
%Y A351448 Cf. A000203, A003958, A005820, A008848, A016754, A231484, A339905, A347391, A351442.
%K A351448 nonn
%O A351448 1,1
%A A351448 _Antti Karttunen_, Feb 12 2022