OFFSET
1,2
LINKS
Robert Price, Table of n, a(n) for n = 1..204226, rows 1-50.
Omar E. Pol, Illustration of the seven regions of 5
FORMULA
EXAMPLE
The first four regions of the section model of partitions are [1],[2, 1],[3, 1, 1],[2]. We can see that there are seven parts so a(4) = 7.
Written as a triangle begins:
1;
3;
6;
7, 12;
13, 20;
21, 23, 24, 35;
36, 38, 39, 54;
55, 57, 58, 62, 63, 64, 86;
87, 89, 90, 94, 95, 97, 98,128;
129,131,132,136,137,138,145,146,148,149,150,192;
193,195,196,200,201,203,204,212,213,214,217,218,219,275;
...
From Omar E. Pol, Oct 20 2014: (Start)
Illustration of initial terms:
. _ _ _ _ _
. _ _ _ |_ _ _ |
. _ _ _ _ |_ _ _|_ |_ _ _|_ |
. _ _ |_ _ | |_ _ | |_ _ | |
. _ _ _ |_ _|_ |_ _|_ | |_ _|_ | |_ _|_ | |
. _ _ |_ _ | |_ _ | |_ _ | | |_ _ | | |_ _ | | |
. _ |_ | |_ | | |_ | | |_ | | | |_ | | | |_ | | | |
. |_| |_|_| |_|_|_| |_|_|_| |_|_|_|_| |_|_|_|_| |_|_|_|_|_|
.
. 1 3 6 7 12 13 20
.
. _ _ _ _ _ _
. _ _ _ |_ _ _ |
. _ _ _ _ |_ _ _|_ |_ _ _|_ |
. _ _ |_ _ | |_ _ | |_ _ | |
. |_ _|_ _ _ |_ _|_ _|_ |_ _|_ _|_ |_ _|_ _|_ |
. |_ _ _ | |_ _ _ | |_ _ _ | |_ _ _ | |
. |_ _ _|_ | |_ _ _|_ | |_ _ _|_ | |_ _ _|_ | |
. |_ _ | | |_ _ | | |_ _ | | |_ _ | | |
. |_ _|_ | | |_ _|_ | | |_ _|_ | | |_ _|_ | | |
. |_ _ | | | |_ _ | | | |_ _ | | | |_ _ | | | |
. |_ | | | | |_ | | | | |_ | | | | |_ | | | | |
. |_|_|_|_|_| |_|_|_|_|_| |_|_|_|_|_| |_|_|_|_|_|_|
.
. 21 23 24 35
(End)
MATHEMATICA
lex[n_]:=DeleteCases[Sort@PadRight[Reverse /@ IntegerPartitions@n], x_ /; x==0, 2];
reg = {}; l = {};
For[j = 1, j <= 56, j++,
mx = Max@lex[j][[j]]; AppendTo[l, mx];
For[i = j, i > 0, i--, If[l[[i]] > mx, Break[]]];
AppendTo[reg, j - i];
];
Accumulate@reg (* Robert Price, Apr 22 2020, revised Jul 25 2020 *)
CROSSREFS
KEYWORD
nonn,tabf
AUTHOR
Omar E. Pol, Apr 23 2012
STATUS
approved