a(n) = tau(n)*Pell(n), where tau(n) = A000005(n), the number of divisors of n.

Terms

a(0) =1a(1) =4a(2) =10a(3) =36a(4) =58a(5) =280a(6) =338a(7) =1632a(8) =2955a(9) =9512a(10) =11482a(11) =83160a(12) =66922a(13) =323128a(14) =780100a(15) =2354160a(16) =2273378a(17) =16465260a(18) =13250218a(19) =95966568a(20) =154455860a(21) =372889432a(22) =450117362a(23) =4346717760a(24) =3935214363a(25) =12667263848a(26) =30581480180a(27) =110745336312a(28) =89120964298