OFFSET
1,2
COMMENTS
LINKS
Ivan Neretin, Table of n, a(n) for n = 1..8192
EXAMPLE
Written as an irregular triangle in which the row lengths are the terms of A011782, the sequence begins:
1;
3;
5,7;
5,11,17,15;
5,11,17,23,29,35,41,31;
5,11,17,23,29,35,41,47,53,59,65,71,77,83,89,63;
5,11,17,23,29,35,41,47,53,59,65,71,77,83,89,95,101,107,113,119,125,131,137,143,149,155,161,167,173,179,185,127;
...
Illustration of initial terms in the fourth quadrant of the square grid:
------------------------------------------------------------------------
n a(n) Compact diagram
------------------------------------------------------------------------
. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
1 1 |_| | | |_ _ | |_ _ _ _ _ _ | |
2 3 |_ _| | |_ | | |_ _ _ _ _ | | |
3 5 |_ _ _| | | | | |_ _ _ _ | | | |
4 7 |_ _ _ _| | | | |_ _ _ | | | | |
5 5 | | |_ _ _| | | |_ _ | | | | | |
6 11 | |_ _ _ _ _| | |_ | | | | | | |
7 17 |_ _ _ _ _ _ _| | | | | | | | | |
8 15 |_ _ _ _ _ _ _ _| | | | | | | | |
9 5 | | | | | | |_ _ _| | | | | | | |
10 11 | | | | | |_ _ _ _ _| | | | | | |
11 17 | | | | |_ _ _ _ _ _ _| | | | | |
12 23 | | | |_ _ _ _ _ _ _ _ _| | | | |
13 29 | | |_ _ _ _ _ _ _ _ _ _ _| | | |
14 35 | |_ _ _ _ _ _ _ _ _ _ _ _ _| | |
15 41 |_ _ _ _ _ _ _ _ _ _ _ _ _ _ _| |
16 31 |_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _|
.
a(n) is also the number of cells in the n-th region of the diagram.
It appears that A241717 can be represented by a similar diagram.
MATHEMATICA
Nest[Join[#, Range[Length[#] - 1]*6 - 1, {2 #[[-1]] + 1}] &, {1}, 7] (* Ivan Neretin, Feb 14 2017 *)
CROSSREFS
KEYWORD
nonn,tabf
AUTHOR
Omar E. Pol, Apr 04 2015
STATUS
approved