login
A200476
Number of partitions of n such that the number of parts and the largest part and the smallest part are pairwise not coprime.
2
0, 0, 0, 1, 0, 1, 0, 3, 1, 3, 1, 8, 3, 9, 6, 16, 9, 24, 17, 35, 29, 49, 45, 81, 73, 110, 115, 166, 166, 240, 250, 347, 372, 491, 539, 715, 776, 988, 1109, 1393, 1553, 1935, 2178, 2676, 3034, 3674, 4176, 5056, 5734, 6862, 7834, 9316, 10615, 12576, 14341, 16890
OFFSET
1,8
COMMENTS
See comments in A199891, which apply to this sequence also.
LINKS
EXAMPLE
a(8) = 3: [2,6], [4,4], [2,2,2,2];
a(9) = 1: [3,3,3];
a(10) = 3: [2,8], [4,6], [2,2,2,4];
a(11) = 1: [2,2,3,4];
a(12) = 8: [2,10], [4,8], [6,6], [3,3,6], [2,2,2,6], [2,2,4,4], [2,3,3,4], [2,2,2,2,2,2].
MAPLE
b:= proc(n, j, t, k) option remember;
add(b(n-i, i, t+1, k), i=j..iquo(n, 2))+
`if`(igcd(n, t)>1 and igcd(k, t)>1 and igcd(n, k)>1, 1, 0)
end:
a:= n-> add(b(n-j, j, 2, j), j=2..iquo(n, 2)):
seq(a(n), n=1..70);
MATHEMATICA
b[n_, j_, t_, k_] := b[n, j, t, k] = Sum[b[n-i, i, t+1, k], {i, j, Quotient[n, 2]}] + If[GCD[n, t]>1 && GCD[k, t]>1 && GCD[n, k]>1, 1, 0]; a[n_] := Sum [b[n-j, j, 2, j], {j, 2, Quotient[n, 2]}]; Table[a[n], {n, 1, 70}] (* Jean-François Alcover, Feb 06 2017, translated from Maple *)
CROSSREFS
Cf. A199891.
Sequence in context: A349619 A082495 A329385 * A300251 A016572 A072860
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Nov 18 2011
STATUS
approved