A105824 - OEIS

%I #29 Nov 07 2017 18:31:16

%S 1,3,0,3,2,0,0,3,1,2,0,0,2,0,0,3,2,3,0,2,0,0,0,0,3,2,0,0,2,0,0,3,0,2,

%T 0,3,2,0,0,2,2,0,0,0,2,0,0,0,1,1,0,2,2,0,0,0,0,2,0,0,2,0,0,3,0,0,0,2,

%U 0,0,0,3,2,2,0,0,0,0,0,2,1,2,0,0,0,0,0,0,2,2,0,0,0,0,0,0,2,3,0,1,2,0,0,2,0

%N a(n) = sigma(n) mod 4.

%H Antti Karttunen, <a href="/A105824/b105824.txt">Table of n, a(n) for n = 1..16384</a>

%H <a href="/index/Su#sums_of_divisors">Index entries for sequences related to sums of divisors</a>

%F a(n) = A010873(A000203(n)). - _Antti Karttunen_, Nov 07 2017

%p A105824:= n-> (numtheory[sigma](n) mod 4):

%p seq (A105824(n), n=1..105); # _Jani Melik_, Jan 26 2011

%t Table[Mod[DivisorSigma[1, n], 4], {n, 100}] (* _Wesley Ivan Hurt_, Nov 07 2017 *)

%o (PARI) a(n)=sigma(n)%4

%Y Cf. A000203, A010873, A248150, A072461, A072462, A191217.

%Y Sequences sigma(n) mod k: A053866 (k=2), A074941 (k=3), A105824 (k=4), A105825 (k=5), A084301 (k=6), A105826 (k=7), A105827 (k=8).

%K easy,nonn

%O 1,2

%A _Shyam Sunder Gupta_, May 05 2005