Total number of parts equal to 1 in all plane partitions of n.

Terms

a(0) =0a(1) =1a(2) =4a(3) =11a(4) =28a(5) =62a(6) =137a(7) =278a(8) =561a(9) =1080a(10) =2051a(11) =3778a(12) =6885a(13) =12255a(14) =21589a(15) =37409a(16) =64160a(17) =108612a(18) =182234a(19) =302461a(20) =497997a(21) =812579a(22) =1316225a(23) =2115608a(24) =3378239a(25) =5357855a(26) =8447086a(27) =13237631a(28) =20632630a(29) =31985504