a(n) = A331456(n)/4.

Terms

a(0) =1a(1) =26a(2) =142a(3) =475a(4) =1202a(5) =2545a(6) =4795a(7) =8283a(8) =13407a(9) =20608a(10) =30362a(11) =43237a(12) =59839a(13) =80792a(14) =106818a(15) =138723a(16) =177369a(17) =223443a(18) =277897a(19) =341823a(20) =416151a(21) =502060a(22) =600640a(23) =713133a(24) =840820a(25) =984678a(26) =1146392a(27) =1327180a(28) =1528184a(29) =1751517