OFFSET
0,2
COMMENTS
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..400
FORMULA
a(n) = 2*Product_{j=1..n-1}(n + 2 - 3*j), n >= 1, (empty product = 1) and a(0) = 1.
E.g.f.: Square of the e.g.f. of A282626 =
2*x + ((1 + sqrt(1-4*x^3))/2)^(2/3) + ((1 - sqrt(1-4*x^3))/2)^(2/3).
MATHEMATICA
Table[If[n==0, 1, 2*Product[n+2-3*j, {j, 1, n-1}]], {n, 0, 25}] (* G. C. Greubel, Mar 29 2019 *)
PROG
(PARI) vector(25, n, n--; if(n==0, 1, 2*prod(j=1, n-1, (n+2-3*j)))) \\ G. C. Greubel, Mar 29 2019
(Magma) [1, 2] cat [2*(&*[n+2-3*j: j in [1..(n-1)]]): n in [2..25]]; // G. C. Greubel, Mar 29 2019
(Sage) [1] + [2*product(n+2-3*j for j in (1..(n-1))) for n in (1..25)] # G. C. Greubel, Mar 29 2019
CROSSREFS
KEYWORD
sign,easy
AUTHOR
Wolfdieter Lang, Mar 04 2017
EXTENSIONS
Terms a(21) onward added by G. C. Greubel, Mar 30 2019
STATUS
approved