a(n) is the number of n-cell polyiamonds (triangular polyominoes) with perimeter n+2.
A131481
a(n) is the number of n-cell polyiamonds (triangular polyominoes) with perimeter n+2.
Terms
- a(0) =1a(1) =1a(2) =1a(3) =3a(4) =4a(5) =11a(6) =23a(7) =62a(8) =149a(9) =409a(10) =1066a(11) =2931a(12) =7981a(13) =22166a(14) =61508a(15) =172267a(16) =483088a(17) =1361475a(18) =3845139a(19) =10894630
External references
- oeis: A131481