Number of vertices on the surface of an icosahedron.

Terms

a(0) =1a(1) =12a(2) =42a(3) =162a(4) =642a(5) =2562a(6) =10242a(7) =40962a(8) =163842a(9) =655362a(10) =2621442a(11) =10485762a(12) =41943042a(13) =167772162a(14) =671088642a(15) =2684354562a(16) =10737418242a(17) =42949672962a(18) =171798691842a(19) =687194767362