A163108 - OEIS

%I #10 Nov 18 2017 09:07:44

%S 1,3,4,3,7,12,7,7,3,12,12,12,7,15,15,3,12,7,12,15,12,13,15,28,3,15,15,

%T 15,15,28,12,12,18,15,18,7,7,28,15,28,15,28,12,28,15,28,18,12,7,7,28,

%U 12,15,31,28,31,18,28,28,31,7,28,15,3,28,24,12,28,28,24,28,15,7,15,12,28,28

%N a(n) = sigma(tau(sigma(n))).

%C Repeated application of tau (number of divisors) and sigma (sum of divisors).

%H Antti Karttunen, <a href="/A163108/b163108.txt">Table of n, a(n) for n = 1..16384</a>

%H <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a>

%F a(n) = A000203(A000005(A000203(n))) = A000203(A062068(n)) = A062069(A000203(n)).

%p with(numtheory) : A163108 := proc(n) sigma(tau(sigma(n))) ; end: seq(A163108(n),n=1..120) ; # _R. J. Mathar_, Jul 27 2009

%o (PARI) A163108(n) = sigma(numdiv(sigma(n))); \\ _Antti Karttunen_, Nov 18 2017

%Y Cf. A000005, A000203, A062068, A062069, A163107.

%K nonn

%O 1,2

%A _Jaroslav Krizek_, Jul 20 2009

%E More terms from _R. J. Mathar_, Jul 27 2009