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 A387160 #16 Aug 26 2025 17:56:52
%S A387160 2,3,7,20,27,28,31,127,496,567,775,2268,3100,8128,8191,27783,131071,
%T A387160 403172,524287,3628548,17389708,32656932,33550336,127926848,
%U A387160 1087307452,1248461136,1408566348,2147483647,7802882100,8589869056,9785767068,10362074688,31211528400,88071903612
%N A387160 Terms of the form prime * m^2 in A351554.
%C A387160 Conjecture: This sequence has no common terms with A228058. See comments in A386430.
%H A387160 <a href="/index/O#opnseqs">Index entries for sequences where odd perfect numbers must occur, if they exist at all</a>
%H A387160 <a href="/index/Pri#prime_indices">Index entries for sequences computed from indices in prime factorization</a>
%H A387160 <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a>
%F A387160 {k | A162642(k) = 1 and A351555(k) = 0}.
%o A387160 (PARI)
%o A387160 A003961(n) = { my(f = factor(n)); for(i=1, #f~, f[i, 1] = nextprime(f[i, 1]+1)); factorback(f); };
%o A387160 A351555(n) = { my(s=sigma(n),f=factor(s),u=A003961(n)); sum(k=1,#f~,if((f[k,1]%2) && 0!=(u%f[k,1]), (valuation(n,f[k,1])!=f[k,2]), 0)); };
%o A387160 isA387160(n) = (isprime(core(n)) && (0==A351555(n)));
%Y A387160 Intersection of A229125 and A351554.
%Y A387160 Cf. A162642, A228058, A351555, A386430.
%Y A387160 Subsequences: A000396\{6}, A000668.
%K A387160 nonn,new
%O A387160 1,1
%A A387160 _Antti Karttunen_, Aug 24 2025
%E A387160 Terms a(29)-a(34) from _Giovanni Resta_, Aug 25 2025