login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A239103 Triangular array read by rows, arising from enumeration of binary words containing n 0's and k 1's that avoid the pattern 1011101. 3
1, 2, 1, 6, 3, 1, 20, 10, 4, 1, 70, 35, 15, 5, 1, 248, 123, 54, 20, 6, 1, 894, 442, 198, 78, 26, 7, 1, 3264, 1611, 732, 300, 108, 33, 8, 1, 12036, 5936, 2727, 1150, 437, 146, 41, 9, 1, 44722, 22047, 10214, 4398, 1736, 617, 192, 50, 10, 1 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Chai Wah Wu, Rows n = 0..15, flattened

D. Baccherini, D. Merlini, R. Sprugnoli, Binary words excluding a pattern and proper Riordan arrays, Discrete Math. 307 (2007), no. 9-10, 1021--1037. MR2292531 (2008a:05003).

EXAMPLE

Triangle begins

1

2 1

6 3 1

20 10 4 1

70 35 15 5 1

248 123 54 20 6 1

894 442 198 78 26 7 1

3264 1611 732 300 108 33 8 1

...

PROG

(Python)

from itertools import combinations

A239103_list = []

for n in range(16):

....for k in range(n, -1, -1):

........c, d0 = 0, ['0']*(n+k)

........for x in combinations(range(n+k), n):

............d = list(d0)

............for i in x:

................d[i] = '1'

............if not '1011101' in ''.join(d):

................c += 1

........A239103_list.append(c) # Chai Wah Wu, Sep 12 2014

CROSSREFS

See A046899 for a closely related triangle. Cf. A246971.

Sequence in context: A180281 A187888 A239102 * A246971 A092392 A128741

Adjacent sequences:  A239100 A239101 A239102 * A239104 A239105 A239106

KEYWORD

nonn,tabl,more

AUTHOR

N. J. A. Sloane, Mar 25 2014

EXTENSIONS

More terms from Chai Wah Wu, Sep 12 2014

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified November 15 14:06 EST 2019. Contains 329149 sequences. (Running on oeis4.)