

A011972


Sequence formed by reading rows of triangle defined in A011971.


4



1, 2, 3, 5, 7, 10, 15, 20, 27, 37, 52, 67, 87, 114, 151, 203, 255, 322, 409, 523, 674, 877, 1080, 1335, 1657, 2066, 2589, 3263, 4140, 5017, 6097, 7432, 9089, 11155, 13744, 17007, 21147, 25287, 30304, 36401, 43833, 52922, 64077, 77821, 94828
(list;
table;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

0,2


COMMENTS

Terms that are repeated in A011971 are included only once, see example. [Joerg Arndt, May 31 2013]


LINKS

Chai Wah Wu, Rows n = 0..200, flattened


EXAMPLE

Triangle A011971 begins:
1;
1, 2;
2, 3, 5;
5, 7, 10, 15;
15, 20,27, 37, 52;
...
Dropping the elements on the diagonal and reading by rows gives this sequence.
 Joerg Arndt, May 31 2013


MATHEMATICA

T[n_, k_] := Sum[Binomial[k, i] BellB[n  k + i + 1], {i, 0, k}];
Table[T[n, k], {n, 0, 8}, {k, 0, n}] // Flatten (* JeanFrançois Alcover, Nov 19 2019 *)


PROG

(Python)
# requires python 3.2 or higher. Otherwise use def'n of accumulate in python docs.
from itertools import accumulate
A011972_list = blist = [1]
for _ in range(10**2):
....b = blist[1]
....blist = list(accumulate([b]+blist))
....A011972_list += blist[1:]
# Chai Wah Wu, Sep 02 2014, updated Chai Wah Wu, Sep 20 2014


CROSSREFS

Sequence in context: A291298 A092021 A022475 * A272402 A321176 A240573
Adjacent sequences: A011969 A011970 A011971 * A011973 A011974 A011975


KEYWORD

nonn,easy,tabl


AUTHOR

N. J. A. Sloane and J. H. Conway


STATUS

approved



