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 A227304 #19 Mar 24 2024 04:00:22
%S A227304 34,55,285,367,835,849,919,1241,1505,2911,2914,3305,4149,4188,6111,
%T A227304 6903,7170,7913,8506,9360,10251,10541,12566,15086,17273,17815,19005,
%U A227304 19689,21411,21462,24882,25020,25501,26610,28125,30361,30593,30789,31485,37741,38211,38983,39787
%N A227304 Numbers k such that sigma(k+1) divides sigma(k-1).
%C A227304 The sequence consists mainly of terms of A055574 = { n | sigma(n+1) = sigma(n-1) }. - _M. F. Hasler_, Aug 06 2015
%H A227304 Amiram Eldar, <a href="/A227304/b227304.txt">Table of n, a(n) for n = 1..6000</a> (term 1..280 from Harvey P. Dale)
%e A227304 Sigma(8507) = 8736 divides sigma(8505) = 17472 = 8736*2, so 8506 is in the sequence.
%t A227304 Flatten[Position[Partition[DivisorSigma[1,Range[40000]],3,1], _?(Divisible[ #[[1]],#[[3]]]&),{1},Heads->False]]+1 (* _Harvey P. Dale_, Jul 15 2014 *)
%Y A227304 Cf. A000203, A055574, A067130, A058073.
%K A227304 nonn
%O A227304 1,1
%A A227304 _Alex Ratushnyak_, Jul 05 2013