a(n) = sigma(n)*Pell(n), where sigma(n) = A000203(n), the sum of divisors of n.

Terms

a(0) =1a(1) =6a(2) =20a(3) =84a(4) =174a(5) =840a(6) =1352a(7) =6120a(8) =12805a(9) =42804a(10) =68892a(11) =388080a(12) =468454a(13) =1938768a(14) =4680600a(15) =14595792a(16) =20460402a(17) =107024190a(18) =132502180a(19) =671765976a(20) =1235646880a(21) =3356004888a(22) =5401408344a(23) =32600383200a(24) =40663881751a(25) =133006270404a(26) =305814801800