a(n) = Sum_{d|n} binomial(n,d)^2.

Terms

a(0) =1a(1) =5a(2) =10a(3) =53a(4) =26a(5) =662a(6) =50a(7) =5749a(8) =7138a(9) =65630a(10) =122a(11) =1151702a(12) =170a(13) =11787102a(14) =9225260a(15) =168963957a(16) =290a(17) =2709216086a(18) =362a(19) =34398664078a(20) =13522807742a(21) =497634360470a(22) =530a(24) =2822797526