A099555 Triangle, read by rows, where T(n,k) = (n-floor(k/2))^k for k = 0..2*n.

1, 1, 1, 1, 2, 1, 1, 1, 3, 4, 8, 1, 1, 1, 4, 9, 27, 16, 32, 1, 1, 1, 5, 16, 64, 81, 243, 64, 128, 1, 1, 1, 6, 25, 125, 256, 1024, 729, 2187, 256, 512, 1, 1, 1, 7, 36, 216, 625, 3125, 4096, 16384, 6561, 19683, 1024, 2048, 1, 1, 1, 8, 49, 343, 1296, 7776, 15625, 78125, 65536

Offset

0,5

Comments

Row functions in y are given by: R_n(y) = Sum_{k=0..2n} (n-floor(k/2))^k*y^k/k!. Evaluated at y=1, the asymptotic behavior of the rows is given by: R_n(1) ~ c*r^n where c = (r+sqrt(r))/(1+2*sqrt(r)) = 0.8957126... and r = 2.0207473586... satisfies r = exp(1/sqrt(r)) -- see A099554 for the decimal expansion of this constant.

Links

Table of n, a(n) for n=0..65.

Formula

E.g.f.: ((1-x*cosh(sqrt(x)*y)) + sqrt(x)*sinh(sqrt(x)*y))/(1+x^2-2*x*cosh(sqrt(x)*y)).

Example

The asymptotic behavior can be demonstrated at the 4th row function:
R_4(y) = 1 + 4*y + 9*y^2/2! + 27*y^3/3! + 16*y^4/4! + 32*y^5/5! + y^6/6! + y^7/7!;
R_4(1) = 14.93492... = (0.895684...)*r^4, where r = 2.0207473586...
Rows begin:
  [1]
  [1, 1],
  [1, 2,  1,   1],
  [1, 3,  4,   8,   1,    1],
  [1, 4,  9,  27,  16,   32,    1,     1],
  [1, 5, 16,  64,  81,  243,   64,   128,    1,     1],
  [1, 6, 25, 125, 256, 1024,  729,  2187,  256,   512,    1,    1],
  [1, 7, 36, 216, 625, 3125, 4096, 16384, 6561, 19683, 1024, 2048, 1, 1],
  ...
which can be derived from the square array A003992:
  [1, 0,  0,   0,   0,    0,     0, ...],
  [1, 1,  1,   1,   1,    1,     1, ...],
  [1, 2,  4,   8,  16,   32,    64, ...],
  [1, 3,  9,  27,  81,  243,   729, ...],
  [1, 4, 16,  64, 256, 1024,  4096, ...],
  [1, 5, 25, 125, 625, 3125, 15625, ...],
  ...
by shifting each column k down by floor(k/2) rows, and omitting the zeros coming from row 0 of A003992.

Prog

(PARI) T(n, k)=(n-k\2)^k

Crossrefs

Cf. A003992, A099554, A099556.

Sequence in context: A122867 A124775 A140075 * A262082 A299045 A124530

Adjacent sequences: A099552 A099553 A099554 * A099556 A099557 A099558

Keyword

nonn,tabf

Author

Paul D. Hanna, Oct 22 2004

Status

approved