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 A307038 #20 Nov 22 2021 10:11:03 %S A307038 1,20,272,65792,2901600,4596800,29016000,4295032832,5789534400, %T A307038 49085337600,585248256000,960935040000 %N A307038 Unitary imperfect numbers: numbers n that equal to their unitary analog of the alternating sum of divisors, A307037(n). %C A307038 Includes all the numbers of the form F(k)*(F(k)-1) with k > 0, where F(k) = 2^(2^k) + 1, the k-th Fermat number, is prime. %C A307038 a(9) > 5*10^9. %C A307038 Also in the sequence are 49085337600, 585248256000, 960935040000 and 46127952000000. %C A307038 a(13) > 2*10^12. - _Giovanni Resta_, Mar 21 2019 %t A307038 f[p_,e_] := p^e + (-1)^e; a[1] = 1; a[n_] := Times @@ f @@@ FactorInteger[n]; Select[Range[10^6], a[#] == # &] %Y A307038 Cf. A000215, A127724 (k-imperfect), A127725 (2-imperfect), A127726 (3-imperfect), A307037. %K A307038 nonn,more %O A307038 1,2 %A A307038 _Amiram Eldar_, Mar 21 2019 %E A307038 a(9)-a(12) from _Giovanni Resta_, Mar 21 2019