This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A284989 Triangle T(n,t) read by rows: the number of n X n {0,1} matrices with trace t where each row sum and each column sum is 2. 3
 1, 0, 0, 0, 0, 1, 1, 0, 3, 2, 9, 24, 24, 24, 9, 216, 540, 610, 420, 210, 44, 7570, 18000, 20175, 13720, 6300, 1920, 265, 357435, 829920, 909741, 617610, 284235, 91140, 19005, 1854, 22040361, 50223600, 54295528, 36663312, 17072790, 5679184, 1337280, 203952, 14833 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 0,9 LINKS Alois P. Heinz, Rows n = 0..14, flattened EXAMPLE 0:         1 1:         0        0 2:         0        0        1 3:         1        0        3        2 4:         9       24       24       24        9 5:       216      540      610      420      210      44 6:      7570    18000    20175    13720     6300    1920     265 7:    357435   829920   909741   617610   284235   91140   19005   1854 8:  22040361 50223600 54295528 36663312 17072790 5679184 1337280 203952 14833 CROSSREFS Cf. A001499 (row sums), A000166 (diagonal), A007107 (column 0). Cf. A008290, A098825, A284990, A284991. Sequence in context: A118791 A234840 A234743 * A049971 A234748 A156528 Adjacent sequences:  A284986 A284987 A284988 * A284990 A284991 A284992 KEYWORD nonn,tabl AUTHOR R. J. Mathar, Apr 07 2017 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 | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.