Number of ways an n-set can be written as the union of 2 sets each with 4 or more elements and whose intersection contains exactly 3 elements.

A349415

Number of ways an n-set can be written as the union of 2 sets each with 4 or more elements and whose intersection contains exactly 3 elements.

Terms

    a(0) =10a(1) =60a(2) =245a(3) =840a(4) =2604a(5) =7560a(6) =20955a(7) =56100a(8) =146146a(9) =372372a(10) =931385a(11) =2293200a(12) =5569880a(13) =13368528a(14) =31751223a(15) =74709900a(16) =174324430a(17) =403700220a(18) =928512277a(19) =2122315800a(20) =4823447300a(21) =10905187800a(22) =24536675475a(23) =54962156340a(24) =122607890874a(25) =272461983780a(26) =603308682865

External references