A330573 a(n) = Sum_{k = 1..ceiling(n/2)} [u_2(k)*u_2(n+1-k)], where u_2(k) is number of unordered factorization k = i*j (A038548).
0, 1, 1, 2, 3, 4, 5, 8, 7, 10, 10, 14, 14, 16, 16, 22, 20, 26, 24, 30, 28, 34, 30, 43, 36, 43, 40, 51, 44, 56, 49, 63, 55, 66, 55, 78, 64, 75, 70, 89, 72, 93, 77, 98, 87, 103, 84, 122, 94, 115, 104, 127, 102, 136, 109, 141, 123, 143, 117, 170, 128, 153, 138, 174, 138, 183, 143, 183, 161, 189, 152, 224, 163, 200, 180
Offset: 0
Keywords
Links
- Amiram Eldar, Table of n, a(n) for n = 0..10000
Programs
-
Mathematica
s[n_] := s[n] = Ceiling[DivisorSigma[0, n]/2]; a[n_] := Sum[s[k]*s[n + 1 - k], {k, 1, Ceiling[n/2]}]; Array[a, 100, 0] (* Amiram Eldar, Apr 19 2024*)
Extensions
Offset and name corrected by Amiram Eldar, Apr 19 2024
Comments