A228166 - OEIS

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A228166

Irregular triangle read by rows: T(n,k) is the number of binary pattern classes in the (7,n)-rectangular grid with k '1's and (7n-k) '0's: two patterns are in same class if one of them can be obtained by a reflection or 180-degree rotation of the other.

1, 1, 4, 12, 19, 19, 12, 4, 1, 1, 4, 28, 94, 266, 508, 777, 868, 777, 508, 266, 94, 28, 4, 1, 1, 8, 65, 363, 1574, 5231, 13826, 29454, 51408, 74130, 88900, 88900, 74130, 51408, 29454, 13826, 5231, 1574, 363, 65, 8, 1, 1, 8, 106, 832, 5199, 24648, 94524, 296296, 777997, 1727440, 3282774, 5369832, 7608483, 9362256, 10032648, 9362256

(list; graph; refs; listen; history; text; internal format)

OFFSET

0,3

COMMENTS

The length of row n is 7*n+1.

Sum of rows (see example) gives A225831.

This triangle is to A225828 as Losanitsch's triangle A034851 is to A005418, triangle A226048 to A225826, triangle A226290 to A225827, triangle A225812 to A225828, triangle A228022 to A225829, and triangle A228165 to A225830.

Also the number of equivalence classes of ways of placing k 1 X 1 tiles in an n X 7 rectangle under all symmetry operations of the rectangle. - Christopher Hunt Gribble, Apr 24 2015

LINKS

Yosu Yurramendi, María Merino, Rows n = 0..20 of irregular triangle, flattened

EXAMPLE

Irregular triangle:

1 4 12 19 19 12 4 1

1 4 28 94 266 508 777 868 777 508 266 94 28 4 1

1 8 65 363 1574 5231 13826 29454 51408 74130 88900 88900 74130 51408 29454 13826 5231 1574 363 65 8 1

CROSSREFS

Cf. A225826-A225829, A005418, A034851, A226048, A226290, A225812, A228022, A228165.

Sequence in context: A307624 A177833 A166162 * A244433 A086109 A275116

Adjacent sequences: A228163 A228164 A228165 * A228167 A228168 A228169

KEYWORD

nonn,tabf

AUTHOR

Yosu Yurramendi, María Merino, Aug 14 2013

EXTENSIONS

Definition corrected by María Merino, May 22 2017

STATUS

approved