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 A108553 Square array, read by antidiagonals, where row n equals the crystal ball sequence for D_n lattice. 12
 1, 1, 1, 1, 3, 1, 1, 5, 5, 1, 1, 13, 13, 7, 1, 1, 25, 55, 25, 9, 1, 1, 41, 169, 147, 41, 11, 1, 1, 61, 411, 625, 309, 61, 13, 1, 1, 85, 853, 2051, 1681, 561, 85, 15, 1, 1, 113, 1583, 5577, 6981, 3721, 923, 113, 17, 1, 1, 145, 2705, 13203, 23673, 18733, 7225, 1415, 145, 19, 1 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 0,5 COMMENTS Rows 0 and 2 are included by extension since they fit the formula. Row 1 equals the odd numbers in order that triangle A108556 maintains that A108556(n,n-1) = (n/2)*A108556(n,n) for all n>=1, where row n of triangle A108556 equals the inverse binomial transform of row n of this square array. LINKS FORMULA T(n, k) = Sum_{j=0..n} C(n+k-j, k-j)*[C(2*n, 2*j) - 2*j*(n-j)*C(n, j)/(n-1)] for n>1, with T(0, k)=1, T(1, k)=2*k+1. EXAMPLE Square array begins: 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,... 1,3,5,7,9,11,13,15,17,19,21,23,25,27,... 1,5,13,25,41,61,85,113,145,181,221,265,... 1,13,55,147,309,561,923,1415,2057,2869,... 1,25,169,625,1681,3721,7225,12769,21025,... 1,41,411,2051,6981,18733,42783,86983,... 1,61,853,5577,23673,76389,204205,476113,... 1,85,1583,13203,68853,264825,824083,... Inverse binomial transform of rows gives rows of triangle A108556: 1, 1,2, 1,4,4, 1,12,30,20, 1,24,120,192,96, 1,40,330,940,1080,432, ... Product of the g.f. of row n and (1-x)^(n+1) generates the symmetric triangle A108558: 1; 1,1; 1,2,1; 1,9,9,1; 1,20,54,20,1; 1,35,180,180,35,1; ... The row sums of triangle A108558 equals the main diagonal of triangle A108556. PROG (PARI) T(n, k)=if(n<0 || k<0, 0, if(n==0 || k==0, 1, if(n==1, 2*k+1, sum(j=0, k, binomial(n+k-j, k-j)*(binomial(2*n, 2*j)-2*n*binomial(n-2, j-1)))))) CROSSREFS Cf. A108554 (diagonal), A108555 (antidiagonal sums), A108556, A108558, A001844 (row 2), A005902 (row 3), A007204 (row 4), A008356 (row 5), A008358 (row 6), A008360 (row 7), A008362 (row 8), A008377 (row 9), A008379 (row 10). Sequence in context: A171229 A125690 A176481 * A176700 A300539 A300966 Adjacent sequences:  A108550 A108551 A108552 * A108554 A108555 A108556 KEYWORD nonn,tabl AUTHOR Paul D. Hanna, Jun 10 2005 STATUS approved

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Last modified May 26 17:16 EDT 2020. Contains 334630 sequences. (Running on oeis4.)