A340275 Number of partitions of n into 3 parts whose smallest two parts are relatively prime.

0, 0, 1, 1, 2, 2, 3, 4, 5, 5, 7, 8, 10, 11, 12, 13, 16, 17, 20, 22, 24, 25, 29, 30, 33, 35, 38, 40, 45, 47, 52, 55, 58, 60, 64, 66, 72, 75, 79, 81, 88, 90, 97, 101, 105, 108, 116, 119, 126, 130, 135, 139, 148, 151, 157, 161, 167, 171, 181, 183, 193, 198, 204, 209, 217, 221

Offset

1,5

Links

Table of n, a(n) for n=1..66.

Index entries for sequences related to partitions

Formula

a(n) = Sum_{k=1..floor(n/3)} Sum_{i=k..floor((n-k)/2)} floor(1/gcd(i,k)).

Mathematica

Table[Sum[Sum[Floor[1/GCD[i, k]], {i, k, Floor[(n - k)/2]}], {k, Floor[n/3]}], {n, 100}]

Crossrefs

Cf. A023023, A340276, A340278.

Sequence in context: A342519 A307780 A340276 * A348323 A367214 A342499

Adjacent sequences: A340272 A340273 A340274 * A340276 A340277 A340278

Keyword

nonn

Author

Wesley Ivan Hurt, Jan 02 2021

Status

approved