A385683 - OEIS

A385683

Complement of A030511.

1, 3, 4, 5, 7, 8, 9, 11, 12, 13, 14, 15, 17, 18, 19, 20, 21, 22, 23, 25, 26, 27, 28, 29, 30, 31, 33, 34, 35, 36, 37, 38, 39, 40, 41, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

COMMENTS

Positive numbers not of the form floor(2*k^2/3).

LINKS

Table of n, a(n) for n=1..67.

FORMULA

a(n) = n+m if n+m>floor(2*(m+1)^2/3) and a(n) = n+m-1 otherwise where m = floor(sqrt(3*(n-1)/2)).

MATHEMATICA

m[n_]:=Floor[Sqrt[3(n-1)/2]]; a[n_]:=If[n+m[n]>Floor[2(m[n]+1)^2/3], n+m[n], n+m[n]-1]; Array[a, 67] (* James C. McMahon, Aug 06 2025 *)

PROG