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 A063977 #7 Jul 22 2024 15:23:35
%S A063977 1,3,4,5,6,8,9,10,12,14,17,18,20,24,26,28,30,32,33,36,38,40,42,44,48,
%T A063977 50,54,56,60,62,65,68,70,72,74,78,80,82,84,90,96,98,100,102,104,108,
%U A063977 110,112,114,120,122,126,128,129,130,132,136,138,140,144,150,152,158
%N A063977 Numbers which are sums of unitary divisors, the usigma values: their inverse usigma set is not empty; usigma() = A034448().
%H A063977 Amiram Eldar, <a href="/A063977/b063977.txt">Table of n, a(n) for n = 1..10000</a>
%t A063977 usigma[n_] := Times @@ (1 + Power @@@ FactorInteger[n]); usigma[1] = 1; seq[max_] := TakeWhile[Union[Array[usigma, max]], # <= max &]; seq[160] (* _Amiram Eldar_, Jul 22 2024 *)
%o A063977 (PARI) usigma(n) = {my(f = factor(n)); prod(i = 1, #f~, 1 + f[i, 1]^f[i, 2]);}
%o A063977 lista(nmax) = Set(select(x -> x <= nmax, vector(nmax, i, usigma(i)))); \\ _Amiram Eldar_, Jul 22 2024
%Y A063977 Cf. A034448, A064000 (complement).
%K A063977 nonn
%O A063977 1,2
%A A063977 _Labos Elemer_, Sep 05 2001