A105824 - OEIS

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A105824

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

11

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, 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, 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

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OFFSET

1,2

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..16384

Index entries for sequences related to sums of divisors

FORMULA

a(n) = A010873(A000203(n)). - Antti Karttunen, Nov 07 2017

MAPLE

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

seq (A105824(n), n=1..105); # Jani Melik, Jan 26 2011

MATHEMATICA

Table[Mod[DivisorSigma[1, n], 4], {n, 100}] (* Wesley Ivan Hurt, Nov 07 2017 *)

PROG

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

CROSSREFS

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

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).

Sequence in context: A298082 A085919 A352613 * A171911 A180193 A229964

Adjacent sequences: A105821 A105822 A105823 * A105825 A105826 A105827

KEYWORD

easy,nonn

AUTHOR

Shyam Sunder Gupta, May 05 2005

STATUS

approved