A128709 O.g.f.: A(x) = 1/(1-1*x/(1-3*x/(1-5*x/(1-7*x/(1-...-(2n-1)*x/(1-...)))))) (continued fraction).

1, 1, 4, 31, 364, 5746, 113944, 2719291, 75843724, 2420160286, 86941080904, 3471911602006, 152562875644984, 7315129181611876, 380045172886143664, 21266347877729314771, 1275148311699896290444, 81563275661324271278566

Offset

0,3

Comments

Hankel transform is A168440. - Paul Barry, Nov 25 2009

Links

Table of n, a(n) for n=0..17.

Formula

a(n) = Sum_{k=0..n} (-1)^k*2^(n-k)*A053979(n,k). - Philippe Deléham, Mar 24 2007

a(n) = Sum_{k=0..n} A094344(n,k)*3^(n-k). - Philippe Deléham, Mar 27 2007

G.f.: 1/(1-x-3x^2/(1-8x-35x^2/(1-16x-99x^2/(1-24x-195x^2/(1-32x-323x^2/(1-... (continued fraction). - Paul Barry, Nov 25 2009

a(n) = top left term of M^n, n > 0; M = the infinite square production matrix:

1, 3, 0, 0, ...

1, 3, 5, 0, ...

1, 3, 5, 7, ...

...

Also, a(n+1) = sum of top row terms of M^n. Example: top row of M^3 = (31, 93, 135, 105, 0, 0, 0, ...), where a(3) = 31 and a(4) = 364 = (31 + 93 + 135 + 105). - Gary W. Adamson, Jul 14 2011

G.f.: 1/T(0) where T(k) = 1 - x*(4*k+1)/(1 - x*(4*k+3)/T(k+1) ); (continued fraction). - Sergei N. Gladkovskii, Mar 19 2013

G.f.: G(0), where G(k) = 1 - x*(2*k+1)/(x*(2*k+1) - 1/G(k+1) ); (continued fraction). - Sergei N. Gladkovskii, Aug 05 2013

a(n) ~ 2^(2*n - 1/2) * (n-1)! / Pi. - Vaclav Kotesovec, Aug 24 2017

Example

G.f.: A(x) = 1 + x + 4x^2 + 31x^3 + 364x^4 + 5746x^5 + ...;
A(x) = 1/(1 - x*(1 + 3x + 24x^2 + 297x^3 + 4896x^4 + ...));
A(x) = 1/(1 - x/(1 - 3x*(1 + 5x + 60x^2 + 1035x^3 + 22500x^4 + ...)));
A(x) = 1/(1 - x/(1 - 3x/(1 - 5x*(1 + 7x + 112x^2 + 2485x^3 + ...)))).

Mathematica

nmax = 20; CoefficientList[Series[1/Fold[(1 - #2/#1) &, 1, Reverse[(2*Range[nmax + 1]-1)*x]], {x, 0, nmax}], x] (* Vaclav Kotesovec, Aug 24 2017 *)

Prog

(PARI) {a(n)=local(CF=1+x*O(x^n)); for(k=0, n, CF=1/(1-(2*n-2*k+1)*x*CF)); polcoeff(CF, n, x)}

Crossrefs

Sequence in context: A016036 A322626 A000314 * A138860 A266757 A369737

Adjacent sequences: A128706 A128707 A128708 * A128710 A128711 A128712

Keyword

nonn

Author

Paul D. Hanna, Mar 23 2007

Status

approved