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 A052396 #12 Aug 26 2022 05:25:29 %S A052396 2,4,8,16,32,63,64,128,256,512,1024,2048,4096,8192,16384,32768,34587, %T A052396 65536,131072,262144,524288,1048576,2097152,4194304,8388608,16777216, %U A052396 33554432,67108864,134217728,170271801,268435456,536870912,1073741824,2147483648,4294967296 %N A052396 (+2)-sigma perfect numbers: numbers k such that (+2)sigma(k) = 2*k, where (+2)sigma(k) = A107758(k). %C A052396 2^n is a term for all n>=1. - _Amiram Eldar_, Aug 26 2022 %e A052396 Factorizations: even examples: 2, 2^2, 2^3, 2^4,...; odd examples: a(6) = 3^2*7, a(17) = 3^4*7*61, a(30) = 3^6*7*61*547. %t A052396 f[p_, e_] := 1 + (p^(e + 1) - 1)/(p - 1); s[n_] := Times @@ f @@@ FactorInteger[n]; s[1] = 1; Select[Range[5*10^6], s[#] == 2*# &] (* _Amiram Eldar_, Aug 26 2022 *) %Y A052396 Cf. A000079, A107758. %K A052396 nonn %O A052396 1,1 %A A052396 _Yasutoshi Kohmoto_ Mar 13 2000 %E A052396 Corrected by _Franklin T. Adams-Watters_, Oct 25 2006 %E A052396 a(30) corrected and a(31)-a(35) added by _Amiram Eldar_, Aug 26 2022