A331075 a(n) = Sum_{k = 1..n} [u_3(k)*u_3(n+1-k)], where u_3 = A034836.

0, 1, 2, 3, 6, 7, 10, 12, 16, 21, 22, 28, 32, 37, 36, 49, 48, 58, 56, 74, 68, 85, 72, 104, 88, 113, 98, 138, 110, 146, 122, 170, 146, 179, 142, 220, 166, 213, 186, 254, 190, 266, 204, 300, 236, 293, 224, 368, 252, 334, 290, 402, 278, 413, 294, 450, 354, 429, 320, 547

Offset

0,3

Comments

For background references see A330570.

Links

Amiram Eldar, Table of n, a(n) for n = 0..10000

Mathematica

s[1] = 1; s[n_] := s[n] = Module[{e = FactorInteger[n][[;; , 2]]}, If[IntegerQ[Surd[n, 3]], 1/3, 0] + (Times @@ ((e + 1)*(e + 2)/2))/6 + (Times @@ (Floor[e/2] + 1))/2]; a[n_] := Sum[s[k] * s[n+1-k], {k, 1, n}]; Array[a, 100, 0] (* Amiram Eldar, Apr 19 2024 *)

Crossrefs

Cf. A034836.

See A331076 for another version.

Sequence in context: A284907 A330572 A287241 * A062720 A069813 A266534

Adjacent sequences: A331072 A331073 A331074 * A331076 A331077 A331078

Keyword

nonn,changed

Author

N. J. A. Sloane, Jan 10 2020

Extensions

Offset corrected by Amiram Eldar, Apr 19 2024

Status

approved