Doubly hexagonal pyramidal numbers.

Terms

a(0) =0a(1) =1a(2) =252a(3) =7337a(4) =84575a(5) =576080a(6) =2795121a(7) =10700382a(8) =34388362a(9) =96606475a(10) =243939410a(11) =564840991a(12) =1217275137a(13) =2469392562a(14) =4757404575a(15) =8765621740a(16) =15534503236a(17) =26603512517a(18) =44196596312a(19) =71459197125a(20) =112756874195a(21) =174046844356a(22) =263335062397a(23) =391232840362a(24) =571628456750a(25) =822490729775