a(0) = 1; a(n) = Sum_{k=1..n} (-1)^(k+1)*d(k+1)*a(n-k), where d() is the number of divisors (A000005).

A307241

a(0) = 1; a(n) = Sum_{k=1..n} (-1)^(k+1)*d(k+1)*a(n-k), where d() is the number of divisors (A000005).

Terms

    a(0) =1a(1) =2a(2) =2a(3) =3a(4) =6a(5) =12a(6) =23a(7) =42a(8) =75a(9) =135a(10) =248a(11) =460a(12) =849a(13) =1554a(14) =2837a(15) =5192a(16) =9527a(17) =17490a(18) =32083a(19) =58809a(20) =107781a(21) =197578a(22) =362280a(23) =664320a(24) =1218069a(25) =2233202a(26) =4094289a(27) =7506602a(28) =13763219a(29) =25234674

External references