Number of side-2 hexagonal 0..n arrays with values nondecreasing E, SW and SE.

Terms

a(0) =10a(1) =53a(2) =200a(3) =606a(4) =1572a(5) =3630a(6) =7656a(7) =15015a(8) =27742a(9) =48763a(10) =82160a(11) =133484a(12) =210120a(13) =321708a(14) =480624a(15) =702525a(16) =1006962a(17) =1418065a(18) =1965304a(19) =2684330a(20) =3617900a(21) =4816890a(22) =6341400a(23) =8261955a(24) =10660806a(25) =13633335a(26) =17289568a(27) =21755800a(28) =27176336a(29) =33715352