A331130 a(n) = Sum_{i=1..n} u_3(i)*u_3(i+1), where u_3(n) = A034836(n).

1, 2, 4, 6, 8, 10, 13, 19, 23, 25, 29, 33, 35, 39, 47, 51, 55, 59, 63, 71, 75, 77, 83, 95, 99, 105, 117, 121, 126, 131, 136, 146, 150, 154, 170, 178, 180, 184, 196, 202, 207, 212, 216, 232, 240, 242, 251, 269, 277, 285, 293, 297, 303, 315, 327, 339, 343, 345, 355, 365

Offset

1,2

Comments

For background references see A330570.

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Mathematica

s[1] = 1; 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]; With[{t = Array[s, 100]}, Accumulate[Most[t] * Rest[t]]] (* Amiram Eldar, Apr 19 2024 *)

Crossrefs

Cf. A034836, A331080.

Sequence in context: A024172 A233735 A085577 * A121832 A253241 A337972

Adjacent sequences: A331127 A331128 A331129 * A331131 A331132 A331133

Keyword

nonn,changed

Author

N. J. A. Sloane, Jan 10 2020

Status

approved