OFFSET
0,2
COMMENTS
An alternative, equivalent, definition: Let T(i) = [1,2,3,...,i*(i+1)/2], and let S be the concatenation of T(1), T(2), ... Create a triangle by partitioning S into rows of lengths 1, 2, 3, ... The right-hand elements of the rows of this triangle form the new sequence.
LINKS
Harvey P. Dale, Table of n, a(n) for n = 0..1000
EXAMPLE
The first few stages in the construction of the triangular array are:
1
then
..1
.1.2.
3
then
...1
..1.2
.3.1.2
3.4.5.6
then
.....1
....1.2
...3.1.2
..3.4.5.6
.1.2.3.4.5
6.7.8.9.10.
The right-most diagonal forms the sequence: 1,2,2,6,5,...
MATHEMATICA
With[{nn=75}, TakeList[Flatten[Range[1, #]&/@Accumulate[Range[nn]]], Range[nn]][[;; , -1]]] (* Harvey P. Dale, Oct 31 2024 *)
CROSSREFS
KEYWORD
easy,nonn,changed
AUTHOR
Floor van Lamoen, Oct 18 2001
EXTENSIONS
Edtied by N. J. A. Sloane, Oct 31 2024
STATUS
approved