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A085521
a(n) = Product_{k=0..n} (2^(2k+1)+1).
1
1, 3, 27, 891, 114939, 58963707, 120816635643, 989850695823099, 32436417451427131131, 4251538544610908358733563, 2229034892015508532492061011707, 4674627210894999765441323226884370171, 39213619892958693087378972992951269575782139, 1315790781385749638968020894900792847245520205672187
OFFSET
-1,2
COMMENTS
Partial products of A087289. - Michel Marcus, Feb 15 2014
LINKS
J. A. Thas, Old and new results on spreads and ovoids of finite classical polar spaces, Annals of Discrete Mathematics, Vol. 52, 1992, pp. 529-544, Combinatorics '90 — Recent Trends and Applications.
FORMULA
a(n) ~ c * 2^(n*(n+2)), where c = 2*QPochhammer(-1/2, 1/4) = 3.5167992012887276... . - Vaclav Kotesovec, Oct 19 2016
MATHEMATICA
Table[Product[2^(2k+1)+1, {k, 0, n}], {n, -1, 15}] (* Harvey P. Dale, Jun 21 2011 *)
Table[QPochhammer[-2, 4, n + 1], {n, -1, 15}] (* Vladimir Reshetnikov, Oct 18 2016 *)
PROG
(PARI) a(n) = prod(k=0, n, 2^(2*k+1)+1); \\ Michel Marcus, Oct 17 2016
CROSSREFS
Sequence in context: A194500 A012505 A331439 * A377760 A009066 A279832
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Jul 03 2003
STATUS
approved