The sum of the first-column lengths of all bargraphs of semiperimeter n (n>=2).

Terms

a(0) =1a(1) =3a(2) =9a(3) =26a(4) =75a(5) =218a(6) =640a(7) =1898a(8) =5682a(9) =17155a(10) =52187a(11) =159827a(12) =492417a(13) =1525222a(14) =4746906a(15) =14837444a(16) =46558573a(17) =146614539a(18) =463186317a(19) =1467631144a(20) =4662899110a(21) =14851847390a(22) =47414162252a(23) =151692982789a(24) =486280700344