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A241603 a(n) = Sum_{d|n, d <= 5} d^2 + 5*Sum_{d|n, d>5} d. 2

%I #13 Mar 18 2015 15:31:55

%S 1,5,10,21,26,44,36,61,55,80,56,120,66,110,110,141,86,179,96,196,150,

%T 170,116,280,151,200,190,266,146,344,156,301,230,260,236,435,186,290,

%U 270,436,206,464,216,406,380,350,236,600,281,455,350,476,266,584,356,586,390,440,296,820,306,470,510,621,416,704,336

%N a(n) = Sum_{d|n, d <= 5} d^2 + 5*Sum_{d|n, d>5} d.

%D P. A. MacMahon, The connexion between the sum of the squares of the divisors and the number of partitions of a given number, Messenger Math., 54 (1924), 113-116. Collected Papers, MIT Press, 1978, Vol. I, pp. 1364-1367.

%H Harvey P. Dale, <a href="/A241603/b241603.txt">Table of n, a(n) for n = 1..1000</a>

%p with(numtheory):

%p A:=proc(s,n) local d,s1,s2;

%p s1:=0; s2:=0;

%p for d in divisors(n) do

%p if d <= s then s1:=s1+d^2 else s2:=s2+d; fi; od:

%p s1+s*s2; end;

%p f:=s->[seq(A(s,n),n=1..80)];

%p f(5);

%t sd5[n_]:=Module[{d=Divisors[n]},Total[Select[d,#<6&]^2]+5Total[Select[ d,#>5&]]]; Array[sd5,70] (* _Harvey P. Dale_, Mar 18 2015 *)

%Y Cf. A002659, A002660.

%Y A row of the array in A242639.

%K nonn

%O 1,2

%A _N. J. A. Sloane_, May 21 2014

%E Typo in definition corrected by _N. J. A. Sloane_, Mar 18 2015

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Last modified April 24 03:08 EDT 2024. Contains 371918 sequences. (Running on oeis4.)