A246021 Number of palstars of length 2n over an alphabet of size 4.

1, 4, 28, 208, 1540, 11440, 84976, 631360, 4690972, 34854352, 258971536, 1924189120, 14296956112, 106228114624, 789287772352, 5864503926016, 43573975930372, 323759929988272, 2405575577105392, 17873718523387456, 132803898120114352, 986749082625941824

Offset

0,2

Links

Lars Blomberg, Table of n, a(n) for n = 0..100

L. Bruce Richmond and J. Shallit, Counting the Palstars, Electronic Journal of Combinatorics, 21(3) (2014), #P3.25.

Prog

(PARI) \\ Richmond and Shallit, Section 2
U(k, size)= { local u; u= vector(size, x, 0); u[1]=1;
for (i = 1, length(u)-1, if(i%2==1, u[i+1]=k*u[i], u[i+1]=k*u[i]-u[i\2+1]));
return(u); }
u = U(4, 101);
p = vector(length(u), x, 0); p[1]=1;
for(n=1, length(u)-1, p[n+1]=sum(i=1, n, u[i+1]*p[n-i+1]));
p \\ Lars Blomberg, Jul 25 2017

Crossrefs

Cf, A246019, A246020.

Sequence in context: A355354 A019482 A198630 * A090965 A106258 A085363

Adjacent sequences: A246018 A246019 A246020 * A246022 A246023 A246024

Keyword

nonn

Author

N. J. A. Sloane, Aug 13 2014

Extensions

a(11)-a(21) from Lars Blomberg, Jul 25 2017

Status

approved