login
Number of partitions of n into 5 squarefree parts.
9

%I #10 Sep 16 2019 21:32:04

%S 0,0,0,0,0,1,1,2,2,4,5,7,7,10,11,15,15,20,22,28,29,37,39,48,49,61,63,

%T 76,77,93,97,113,115,135,140,161,164,190,196,224,228,261,269,304,308,

%U 351,360,404,412,462,475,528,538,597,612,675,685,759,774,849

%N Number of partitions of n into 5 squarefree parts.

%H <a href="/index/Par#part">Index entries for sequences related to partitions</a>

%F a(n) = Sum_{l=1..floor(n/5)} Sum_{k=l..floor((n-l)/4)} Sum_{j=k..floor((n-k-l)/3)} Sum_{i=j..floor((n-j-k-l)/2)} mu(l)^2 * mu(k)^2 * mu(j)^2 * mu(i)^2 * mu(n-i-j-k-l)^2, where mu is the Möbius function (A008683).

%F a(n) = A308839(n)/n.

%e The partitions of n into 5 parts for n = 10, 11, ..

%e 1+1+1+1+10

%e 1+1+1+2+9

%e 1+1+1+3+8

%e 1+1+1+4+7

%e 1+1+1+5+6

%e 1+1+1+1+9 1+1+2+2+8

%e 1+1+1+2+8 1+1+2+3+7

%e 1+1+1+3+7 1+1+2+4+6

%e 1+1+1+4+6 1+1+2+5+5

%e 1+1+1+5+5 1+1+3+3+6

%e 1+1+1+1+8 1+1+2+2+7 1+1+3+4+5

%e 1+1+1+2+7 1+1+2+3+6 1+1+4+4+4

%e 1+1+1+3+6 1+1+2+4+5 1+2+2+2+7

%e 1+1+1+1+7 1+1+1+4+5 1+1+3+3+5 1+2+2+3+6

%e 1+1+1+2+6 1+1+2+2+6 1+1+3+4+4 1+2+2+4+5

%e 1+1+1+3+5 1+1+2+3+5 1+2+2+2+6 1+2+3+3+5

%e 1+1+1+1+6 1+1+1+4+4 1+1+2+4+4 1+2+2+3+5 1+2+3+4+4

%e 1+1+1+2+5 1+1+2+2+5 1+1+3+3+4 1+2+2+4+4 1+3+3+3+4

%e 1+1+1+3+4 1+1+2+3+4 1+2+2+2+5 1+2+3+3+4 2+2+2+2+6

%e 1+1+2+2+4 1+1+3+3+3 1+2+2+3+4 1+3+3+3+3 2+2+2+3+5

%e 1+1+2+3+3 1+2+2+2+4 1+2+3+3+3 2+2+2+2+5 2+2+2+4+4

%e 1+2+2+2+3 1+2+2+3+3 2+2+2+2+4 2+2+2+3+4 2+2+3+3+4

%e 2+2+2+2+2 2+2+2+2+3 2+2+2+3+3 2+2+3+3+3 2+3+3+3+3

%e --------------------------------------------------------------------------

%e n | 10 11 12 13 14 ...

%e --------------------------------------------------------------------------

%e a(n) | 5 7 7 10 11 ...

%e --------------------------------------------------------------------------

%e - _Wesley Ivan Hurt_, Sep 16 2019

%t Table[Sum[Sum[Sum[Sum[MoebiusMu[l]^2*MoebiusMu[k]^2*MoebiusMu[j]^2* MoebiusMu[i]^2*MoebiusMu[n - i - j - k - l]^2, {i, j, Floor[(n - j - k - l)/2]}], {j, k, Floor[(n - k - l)/3]}], {k, l, Floor[(n - l)/4]}], {l, Floor[n/5]}], {n, 0, 80}]

%Y Cf. A008683, A308839.

%K nonn

%O 0,8

%A _Wesley Ivan Hurt_, Jun 28 2019