Fermat coefficients.

Terms

a(0) =1a(1) =9a(2) =42a(3) =132a(4) =334a(5) =728a(6) =1428a(7) =2584a(8) =4389a(9) =7084a(10) =10963a(11) =16380a(12) =23751a(13) =33563a(14) =46376a(15) =62832a(16) =83657a(17) =109668a(18) =141778a(19) =181001a(20) =228459a(21) =285384a(22) =353127a(23) =433160a(24) =527085a(25) =636636a(26) =763686a(27) =910252a(28) =1078500a(29) =1270752