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 A387712 #10 Sep 06 2025 13:55:45
%S A387712 4,18,27,30,42,45,50,63,66,70,78,102,114,138,174,186,222,246,258,282,
%T A387712 318,354,366,375,402,426,438,474,498,525,534,582,606,618,625,642,654,
%U A387712 678,686,735,762,786,822,825,834,894,906,942,975,978,1002,1038,1074,1078,1086,1089,1146,1158,1182,1194,1210,1266,1274,1275
%N A387712 Primitive terms of A387711: numbers k for which A003959(k) > 2*k, but for all whose proper divisors d|k, d<k, A003959(d) <= 2*d.
%H A387712 Antti Karttunen, <a href="/A387712/b387712.txt">Table of n, a(n) for n = 1..10000</a>
%F A387712 {k | A387715(k) == 1}.
%o A387712 (PARI)
%o A387712 A003959(n) = { my(f = factor(n)); for(i=1, #f~, f[i, 1]++); factorback(f); };
%o A387712 A387715(n) = sumdiv(n,d,(A003959(d)>(2*d)));
%o A387712 is_A387712(n) = (1==A387715(n));
%Y A387712 Cf. A003959, A387711, A387713.
%Y A387712 Positions of 1's in A387715.
%Y A387712 Cf. also A091191, A337372.
%K A387712 nonn,new
%O A387712 1,1
%A A387712 _Antti Karttunen_, Sep 06 2025