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 A105626 Triangular matrix T, read by rows, that satisfies T^2 = A105615^3; also equals the matrix cube of triangle A105623. 2
 1, 3, 1, 18, 6, 1, 150, 48, 9, 1, 1566, 480, 93, 12, 1, 19494, 5736, 1125, 153, 15, 1, 280998, 79584, 15681, 2190, 228, 18, 1, 4598910, 1256808, 247929, 35181, 3780, 318, 21, 1, 84237246, 22262640, 4389213, 629424, 68961, 6000, 423, 24, 1, 1707637734 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS SHIFT_LEFT(column 0 of T) = 3*(column 2 of A105615). A105623 equals the matrix square-root of triangle A105615. LINKS FORMULA T(n+1, 0) = 3*A105615(n+2, 2) = 3*A105617(n) for n>=0. EXAMPLE Triangle begins: 1; 3,1; 18,6,1; 150,48,9,1; 1566,480,93,12,1; 19494,5736,1125,153,15,1; 280998,79584,15681,2190,228,18,1; 4598910,1256808,247929,35181,3780,318,21,1; 84237246,22262640,4389213,629424,68961,6000,423,24,1; ... PROG (PARI) T(n, k)=local(R, M=matrix(n+1, n+1, m, j, if(m>=j, if(m==j, 1, if(m==j+1, -2*j, polcoeff(1/sum(i=0, m-j, (2*i)!/i!/2^i*x^i)+O(x^m), m-j)))))^-3); R=(M+M^0)/2; for(i=1, floor(2*log(n+2)), R=(R+M*R^(-1))/2); return(if(n

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Last modified January 23 01:37 EST 2021. Contains 340384 sequences. (Running on oeis4.)