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A097012 a(n) = sigma(n) mod 210. 5

%I

%S 1,3,4,7,6,12,8,15,13,18,12,28,14,24,24,31,18,39,20,42,32,36,24,60,31,

%T 42,40,56,30,72,32,63,48,54,48,91,38,60,56,90,42,96,44,84,78,72,48,

%U 124,57,93,72,98,54,120,72,120,80,90,60,168,62,96,104,127,84,144,68,126,96

%N a(n) = sigma(n) mod 210.

%C Agrees with A000203(n) for n <= 89; sigma(90) = 234. - _Omar E. Pol_, Feb 02 2013

%C This sequence is not multiplicative. For example, at a(84) = 14 which is not a(3)*a(4)*a(7) = 224. - _Andrew Howroyd_, Aug 23 2018

%H Michael De Vlieger, <a href="/A097012/b097012.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) = A000203(n) mod 210.

%t Array[Mod[DivisorSigma[1, #], 210] &, 69] (* _Michael De Vlieger_, Jul 24 2017 *)

%o (PARI) a(n) = sigma(n) % 210; \\ _Michel Marcus_, Dec 19 2013

%o (MAGMA) [SumOfDivisors(n) mod 210: n in [1..70]]; // _Vincenzo Librandi_, Jul 25 2017

%Y Cf. A000203, A084301, A084303, A097011, A097013, A097014, A097015.

%K nonn

%O 1,2

%A _Labos Elemer_, Aug 19 2004

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Last modified March 1 02:43 EST 2021. Contains 341732 sequences. (Running on oeis4.)