a(n) is the number of five element sets of distinct integer-sided trapezoids whose base angles are 60 degrees that fill an equilateral triangular grid of side n units.

A391498

a(n) is the number of five element sets of distinct integer-sided trapezoids whose base angles are 60 degrees that fill an equilateral triangular grid of side n units.

Terms

    a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =2a(6) =20a(7) =83a(8) =199a(9) =422a(10) =746a(11) =1255a(12) =1940a(13) =2900a(14) =4136a(15) =5752a(16) =7768a(17) =10273a(18) =13330a(19) =17022a(20) =21411a(21) =26586a(22) =32674a(23) =39682a(24) =47823a(25) =57073a(26) =67656a(27) =79598a(28) =93119a(29) =108109

External references