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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 (* Jean-Fran├žois 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

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Last modified February 17 18:14 EST 2020. Contains 332005 sequences. (Running on oeis4.)