A105853 - OEIS

%I #18 May 20 2019 10:28:45

%S 1,3,4,7,6,2,8,5,3,8,2,8,4,4,4,1,8,9,0,2,2,6,4,0,1,2,0,6,0,2,2,3,8,4,

%T 8,1,8,0,6,0,2,6,4,4,8,2,8,4,7,3,2,8,4,0,2,0,0,0,0,8,2,6,4,7,4,4,8,6,

%U 6,4,2,5,4,4,4,0,6,8,0,6,1,6,4,4,8,2,0,0,0,4,2,8,8,4,0,2,8,1,6,7,2,6,4,0,2

%N a(n) = sigma(n) (mod 10), i.e., unit's digit of sigma(n).

%H Antti Karttunen, <a href="/A105853/b105853.txt">Table of n, a(n) for n = 1..20000</a>

%F a(n) = A010879(A000203(n)). - _Michel Marcus_, Jul 26 2017

%p A105853:=n->(numtheory)[sigma](n) mod 10: seq(A105853(n), n=1..180); # _Wesley Ivan Hurt_, Nov 07 2017

%t Mod[DivisorSigma[1,Range[110]],10] (* _Harvey P. Dale_, May 20 2019 *)

%o (PARI) a(n)=sigma(n)%10

%Y Cf. A000203, A010879.

%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), A105852 (k=9), A105853 (k=10).

%K easy,nonn,base

%O 1,2

%A _Shyam Sunder Gupta_, May 05 2005