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 A262520 #8 Oct 03 2015 08:43:40 %S A262520 1,1,1,2,0,1,2,1,1,3,2,3,0,3,4,5,4,5,3,5,6,7,5,6,1,6,7,7,8,8,10,7,2, %T A262520 10,9,10,13,9,11,12,1,1,4,1,3,3,2,3,7,2,2,5,7,4,9,5,6,5,5,5,6,5,1,3,7, %U A262520 2,8,1,8,3,9,3,3,2,3,5,3,4,6,4,6,7,4,6,2,6,6,1,7,7,10,8,9,8,8,9,10,8,1,10,10,10,11,9,11,12,10,12,13,12,13,13,-2,-1,2,13,13,14,14,15 %N A262520 a(n) = A262519(n) - A262518(n). %C A262520 a(n) = How many steps more are needed to reach zero when starting from k = 2*n + 1 than when starting from k = 2*n and repeatedly applying the map that replaces k by k - d(k)? [Here d(k) is the number of divisors of k (A000005)]. If it takes more steps when starting from 2n than from 2n+1, then a(n) is negative. %H A262520 Antti Karttunen, <a href="/A262520/b262520.txt">Table of n, a(n) for n = 0..10000</a> %F A262520 a(n) = A262519(n) - A262518(n). %o A262520 (Scheme) (define (A262520 n) (- (A262519 n) (A262518 n))) %Y A262520 Cf. A000005, A049820, A155043, A262518, A262519, A262521 (positions of negative values). %K A262520 sign %O A262520 0,4 %A A262520 _Antti Karttunen_, Oct 02 2015