Number of stacks, or arrangements of n pennies in contiguous rows, each touching 2 in row below.

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =3a(5) =5a(6) =8a(7) =12a(8) =18a(9) =26a(10) =38a(11) =53a(12) =75a(13) =103a(14) =142a(15) =192a(16) =260a(17) =346a(18) =461a(19) =607a(20) =797a(21) =1038a(22) =1348a(23) =1738a(24) =2234a(25) =2856a(26) =3638a(27) =4614a(28) =5832a(29) =7342