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 A324898 #26 Dec 15 2021 13:26:29 %S A324898 236925,3847725,51122925,69468525,151141725,154669725,269748225, %T A324898 344211525,415565325,445817925,551569725,1111904325,1112565825, %U A324898 1113756525,1175717025,1400045625,1631666925,1695170925,1820873925,1915847325,1946981925,2179080225,2321121825,2453690925,2460041325,2491740225,3223500525,3493517445,3775103325 %N A324898 Odd numbers k such that sigma(k) is congruent to 2 modulo 4 and k = A318458(k), where A318458(k) is bitwise-AND of k and sigma(k)-k. %C A324898 If this sequence has no common terms with A324647, or no terms common with A324727, then there are no odd perfect numbers. %C A324898 The first 29 terms factored: %C A324898 236925 = 3^6 * 5^2 * 13, %C A324898 3847725 = 3^2 * 5^2 * 7^2 * 349, %C A324898 51122925 = 3^2 * 5^2 * 7^2 * 4637, %C A324898 69468525 = 3^2 * 5^2 * 7^2 * 6301, %C A324898 151141725 = 3^2 * 5^2 * 7^2 * 13709, %C A324898 154669725 = 3^2 * 5^2 * 7^2 * 14029, %C A324898 269748225 = 3^6 * 5^2 * 19^2 * 41, %C A324898 344211525 = 3^4 * 5^2 * 7^2 * 3469, %C A324898 415565325 = 3^2 * 5^2 * 7^2 * 37693, %C A324898 445817925 = 3^4 * 5^2 * 7^2 * 4493, %C A324898 551569725 = 3^2 * 5^2 * 7^4 * 1021, %C A324898 1111904325 = 3^2 * 5^2 * 7^2 * 100853, %C A324898 1112565825 = 3^2 * 5^2 * 7^2 * 100913, %C A324898 1113756525 = 3^2 * 5^2 * 7^2 * 101021, %C A324898 1175717025 = 3^4 * 5^2 * 7^2 * 17^2 * 41, %C A324898 1400045625 = 3^2 * 5^4 * 11^4 * 17, %C A324898 1631666925 = 3^2 * 5^2 * 7^2 * 147997, %C A324898 1695170925 = 3^2 * 5^2 * 7^2 * 153757, %C A324898 1820873925 = 3^4 * 5^2 * 13 * 263^2, [Here the unitary prime is not the largest] %C A324898 1915847325 = 3^2 * 5^2 * 7^2 * 173773, %C A324898 1946981925 = 3^2 * 5^2 * 7^2 * 176597, %C A324898 2179080225 = 3^4 * 5^2 * 7^2 * 21961, %C A324898 2321121825 = 3^4 * 5^2 * 11^2 * 9473, %C A324898 2453690925 = 3^2 * 5^2 * 7^2 * 222557, %C A324898 2460041325 = 3^2 * 5^2 * 7^2 * 223133, %C A324898 2491740225 = 3^6 * 5^2 * 13^2 * 809, %C A324898 3223500525 = 3^2 * 5^2 * 7^2 * 292381, %C A324898 3493517445 = 3^6 * 5^1 * 11^2 * 89^2, [Here the unitary prime is not the largest] %C A324898 3775103325 = 3^2 * 5^2 * 7^2 * 342413. %C A324898 Subsequence of A228058 provided this sequence does not contain any prime powers. - _Antti Karttunen_, Jun 17 2019 %C A324898 Sequence contains no prime powers up to 10^20. I believe any prime powers must be of the form (4k+1)^(4e+1), in which case I have verified this up to 10^50. - _Charles R Greathouse IV_, Dec 08 2021 %H A324898 <a href="/index/Bi#binary">Index entries for sequences related to binary expansion of n</a> %H A324898 <a href="/index/O#opnseqs">Index entries for sequences where any odd perfect numbers must occur</a> %H A324898 <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a> %t A324898 Select[Range[10^5, 10^8, 2], And[Mod[#2, 4] == 2, BitAnd[#1, #2 - #1] == #1] & @@ {#, DivisorSigma[1, #]} &] (* _Michael De Vlieger_, Jun 22 2019 *) %o A324898 (PARI) for(n=1, oo, if((n%2)&&2==((t=sigma(n))%4)&&(bitand(n, t-n)==n), print1(n,", "))); %Y A324898 Intersection of A191218 and A324897, also intersection of A191218 and A324649. %Y A324898 Cf. A228058, A318458, A324647, A324727. %K A324898 nonn %O A324898 1,1 %A A324898 _Antti Karttunen_, Apr 19 2019