A359435 a(n) = binomial(2*n-1,n) - n^2 - 1.

0, 18, 100, 425, 1666, 6370, 24228, 92277, 352594, 1351933, 5200130, 20058103, 77558534, 300539938, 1166802820, 4537567325, 17672631538, 68923264009, 269128936778, 1052049481375, 4116715363270, 16123801840973, 63205303218250, 247959266473375, 973469712823326

Offset

3,2

Comments

a(n) is the number of ways to place n indistinguishable balls into n distinguishable boxes with at least 2 boxes remaining empty and not all balls placed in one box.

Links

Table of n, a(n) for n=3..27.

Mathematica

Table[Binomial[2*n - 1, n] - n^2 - 1, {n, 3, 30}] (* Wesley Ivan Hurt, Jan 20 2024 *)

Crossrefs

Cf. A352027.

Sequence in context: A231144 A259231 A064604 * A301542 A231138 A140198

Adjacent sequences: A359432 A359433 A359434 * A359436 A359437 A359438

Keyword

nonn,easy

Author

Enrique Navarrete, Dec 31 2022

Status

approved