Number of unordered pairs of distinct integer partitions of n.

Terms

a(0) =0a(1) =0a(2) =1a(3) =3a(4) =10a(5) =21a(6) =55a(7) =105a(8) =231a(9) =435a(10) =861a(11) =1540a(12) =2926a(13) =5050a(14) =9045a(15) =15400a(16) =26565a(17) =43956a(18) =73920a(19) =119805a(20) =196251a(21) =313236a(22) =501501a(23) =786885a(24) =1239525a(25) =1915903a(26) =2965830a(27) =4528545a(28) =6909903a(29) =10417330