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 A219544 #12 Mar 20 2021 10:55:12 %S A219544 3,14,60,248,336,4064,15120,16380,261888,1089270,11784960,16775168, %T A219544 22766400,71495424,229909120,689727360,738152448,4294934528, %U A219544 7091219520,15999197760,21930739200,25500590080,33216860160 %N A219544 Even multiply-perfect numbers divided by 2. %C A219544 Just as no odd perfect number is known, all known multiply-perfect numbers A007691 greater than 1 are even. %C A219544 The subsequence of even perfect numbers divided by 2 is A133028. %C A219544 The subsequence of even triperfects / 2 is A326051. - _Antti Karttunen_, Mar 20 2021 %D A219544 R. K. Guy, Unsolved Problems in Number Theory, B2. %F A219544 a(n) = A007691(n+1)/2. %F A219544 a(n) = A194771(n+1)/4. [provided there are no odd multiperfect numbers > 1] - _Antti Karttunen_, Mar 20 2021 %Y A219544 Cf. A007691, A133028, A194771, A326051. %K A219544 nonn %O A219544 1,1 %A A219544 _Jonathan Sondow_, Nov 22 2012