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A226239 Minimum m such that there exists an n-row subtractive triangle with distinct integers in 1..m. 0
1, 3, 6, 10, 15, 22, 33, 44, 59, 76, 101, 125 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

In an n-row subtractive triangle, there are n-i+1 integers in the i-th row. The integers in the first row are arbitrary. From the next row, the integers are the absolute difference between adjacent integers in the previous row.

LINKS

Table of n, a(n) for n=1..12.

Chyanog, A Chinese web page where the problem came out

EXAMPLE

a(6)=22 because there is a 6-row subtractive triangle with distinct integers in [1..22] as follows:

1:  6 20 22  3 21 13

2: 14  2 19 18  8

3: 12 17  1 10

4:  5 16  9

5: 11  7

6:  4

However, there is no such triangle with distinct integers in [1..21].

CROSSREFS

Cf. A035313, A035312.

Sequence in context: A122047 A177100 A265071 * A209231 A137358 A143963

Adjacent sequences:  A226236 A226237 A226238 * A226240 A226241 A226242

KEYWORD

nonn,hard,more

AUTHOR

Yi Yang, Jun 01 2013

EXTENSIONS

a(12) from Yi Yang, Mar 04 2015

STATUS

approved

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Last modified October 18 00:55 EDT 2019. Contains 328135 sequences. (Running on oeis4.)