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 A015889 #14 Aug 13 2021 10:48:13 %S A015889 1,2,4,10,20,52,130,370,1066,1090,2626,4580,7540,9140,21268,21682, %T A015889 24634,26596,29380,38740,40330,65026,146810,152164,154180,159172, %U A015889 211492,271426,290116,330706,432730,567988,575956,710788,782090 %N A015889 Numbers k that divide 4^k + 4. %H A015889 Giovanni Resta, <a href="/A015889/b015889.txt">Table of n, a(n) for n = 1..750</a> %t A015889 Select[Range[800000],Divisible[4^#+4,#]&] (* _Harvey P. Dale_, Jun 06 2012 *) %Y A015889 Cf. A006517, A015888, A015891, A015892, A015893, A015897, A015898, A015902, A015903, A015904, A015905, A015906. %K A015889 nonn %O A015889 1,2 %A A015889 _Robert G. Wilson v_ %E A015889 Corrected (a(2) = 2 inserted) by _Harvey P. Dale_, Jun 06 2012