The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A059678 Triangle T(n,k) giving number of fixed 2 X k polyominoes with n cells (n >= 2, 1<=k<=n-1). 5
 1, 0, 4, 0, 1, 8, 0, 0, 6, 12, 0, 0, 1, 18, 16, 0, 0, 0, 8, 38, 20, 0, 0, 0, 1, 32, 66, 24, 0, 0, 0, 0, 10, 88, 102, 28, 0, 0, 0, 0, 1, 50, 192, 146, 32, 0, 0, 0, 0, 0, 12, 170, 360, 198, 36, 0, 0, 0, 0, 0, 1, 72, 450, 608, 258, 40, 0, 0, 0, 0, 0, 0, 14, 292, 1002, 952, 326, 44, 0, 0, 0 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 2,3 LINKS Andrew Howroyd, Table of n, a(n) for n = 2..1276 R. C. Read, Contributions to the cell growth problem, Canad. J. Math., 14 (1962), 1-20. FORMULA T(n, k) = Sum_v C(n-k+1, 2*k-n-v)*C(n-k+v, n-k). G.f. (1+x*y)^2/(1-x*y)*1/((1-x*y)-(1+x*y)*x^2*y). - Christopher Hanusa (chanusa(AT)math.washington.edu), Sep 22 2004 T(n,k) = 0 for n > 2*k. - Andrew Howroyd, Oct 02 2017 EXAMPLE Triangle begins: 1; 0, 4; 0, 1, 8; 0, 0, 6, 12; 0, 0, 1, 18, 16; 0, 0, 0,  8, 38, 20; 0, 0, 0,  1, 32, 66, 24; ... MAPLE with(combinat): for n from 2 to 30 do for k from 1 to n-1 do printf(`%d, `, sum(binomial(n-k+1, 2*k-n-v)*binomial(n-k+v, n-k), v=0..k) ) od:od: MATHEMATICA t[n_, k_] := Sum[Binomial[n-k+1, 2*k-n-v]*Binomial[n-k+v, n-k], {v, 0, k}]; Table[t[n, k], {n, 2, 15}, {k, 1, n-1}] // Flatten (* Jean-François Alcover, Dec 20 2013 *) CROSSREFS Column sums are A034182. Cf. A059679, A059680, A059681, A059682. Sequence in context: A334385 A201560 A255644 * A079642 A342911 A221483 Adjacent sequences:  A059675 A059676 A059677 * A059679 A059680 A059681 KEYWORD nonn,easy,nice,tabl AUTHOR N. J. A. Sloane, Feb 05 2001 EXTENSIONS More terms from James A. Sellers, Feb 06 2001 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.

Last modified April 22 07:26 EDT 2021. Contains 343163 sequences. (Running on oeis4.)