Centered pentagonal numbers: (5n^2+5n+2)/2; crystal ball sequence for 3.3.3.4.4. planar net.

Terms

a(0) =1a(1) =6a(2) =16a(3) =31a(4) =51a(5) =76a(6) =106a(7) =141a(8) =181a(9) =226a(10) =276a(11) =331a(12) =391a(13) =456a(14) =526a(15) =601a(16) =681a(17) =766a(18) =856a(19) =951a(20) =1051a(21) =1156a(22) =1266a(23) =1381a(24) =1501a(25) =1626a(26) =1756a(27) =1891a(28) =2031a(29) =2176