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A246019 Number of palstars of length 2n over an alphabet of size 2. 3
1, 2, 6, 20, 66, 220, 732, 2440, 8134, 27124, 90452, 301656, 1006036, 3355224, 11190040, 37320144, 124467394, 415114844, 1384462172, 4617363016, 15399513116, 51359405064, 171290386824, 571276030192, 1905280915036, 6354363191688, 21192639534984, 70680248726256 (list; graph; refs; listen; history; text; internal format)
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(2, 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. A246020, A246021.

Sequence in context: A174846 A111285 A052991 * A226510 A108627 A193234

Adjacent sequences:  A246016 A246017 A246018 * A246020 A246021 A246022

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Aug 13 2014

EXTENSIONS

Typo in name fixed by Jeffrey Shallit, Aug 14 2014

a(11)-a(18) from Lars Blomberg, Jul 25 2017

STATUS

approved

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Last modified August 22 11:34 EDT 2019. Contains 326176 sequences. (Running on oeis4.)