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 A189825 #8 Mar 30 2012 17:22:58
%S A189825 2,4,3,14,5,7,15,11,17,19,35,29,65,41,101,79,143,71,197,161,323,169,
%T A189825 2917,181,577,239,575,629,899,419,1297,701,901,721,25599,881,5183,
%U A189825 1121,9215,2351,4901,1079,107585,1681,36863,2159,3601,2881,11663,2519
%N A189825 Least number k such that d(k-1) + d(k+1) = n, where d(k) is the number of divisors of k.
%C A189825 The function d(k-1) + d(k+1) is a measure of the compositeness of the numbers next to k. There is no k for n=1 and n=2. Some terms can be quite large; for example, a(99) = 6533135.
%H A189825 Donovan Johnson, <a href="/A189825/b189825.txt">Table of n, a(n) for n = 3..880</a>
%F A189825 Least k such that A189827(k) = n.
%t A189825 nn = 100; t = Table[-1, {nn}]; t[[1]] = t[[2]] = 0; cnt = 2; n = 1; While[cnt < nn, n++; s = DivisorSigma[0,n-1] + DivisorSigma[0,n+1]; If[s <= nn && t[[s]] == -1, t[[s]] = n; cnt++]]; Drop[t,2]
%Y A189825 Cf. A175144.
%K A189825 nonn
%O A189825 3,1
%A A189825 _T. D. Noe_, Apr 28 2011