A111407 - OEIS

%I #18 Jun 25 2022 21:43:42

%S 1,1,0,0,0,1,-1,1,-1,1,-1,2,-2,1,0,-1,0,2,-2,2,-1,0,-1,2,-2,1,0,1,-2,

%T 2,-2,2,-1,0,0,0,-1,1,0,1,-2,2,-2,2,0,-1,-1,2,-2,2,-1,1,-2,2,-1,1,-1,

%U 0,-1,4,-4,1,1,-2,1,1,-2,2,-1,1,-2,4,-4,1,1,0,-1,1,-2,2,-2,1,-1,4,-3,0,0,1,-2,4,-3,1,-1,0,0,3,-4,2,0,-1,-1

%N a(n) = f(f(n+1)) - f(f(n)), where f(0) = 0 and f(m) = tau(m) = A000005(m) for m > 0.

%H Antti Karttunen, <a href="/A111407/b111407.txt">Table of n, a(n) for n = 0..20000</a>

%o (PARI)

%o f = numdiv;

%o a(n) = f(f(n+1)) - f(f(n));

%o concat([1], vector(166,n,a(n))) \\ _Joerg Arndt_, Jul 06 2013

%o (PARI)

%o f(n) = if(!n,n,numdiv(n));

%o A111407(n) = f(f(n+1)) - f(f(n)); \\ _Antti Karttunen_, Oct 07 2017

%Y Cf. A000005, A111405.

%Y First differences of A010553.

%K sign

%O 0,12

%A _N. J. A. Sloane_, Nov 12 2005

%E Description clarified by _Antti Karttunen_, Oct 07 2017