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 A341543 a(n) = sqrt( Product_{j=1..n} Product_{k=1..2} (4*sin((2*j-1)*Pi/(2*n))^2 + 4*sin((2*k-1)*Pi/2)^2) ). 1
 8, 36, 200, 1156, 6728, 39204, 228488, 1331716, 7761800, 45239076, 263672648, 1536796804, 8957108168, 52205852196, 304278005000, 1773462177796, 10336495061768, 60245508192804, 351136554095048, 2046573816377476, 11928306344169800 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Index entries for linear recurrences with constant coefficients, signature (7, -7, 1) FORMULA a(n) = 7*a(n-1) - 7*a(n-2) + a(n-3). a(n) = 6*a(n-1) - a(n-2) - 8. a(n) = 2*(A001541(n) + 1). - Hugo Pfoertner, Feb 14 2021 G.f.: 4*x*(2 - 5*x + x^2)/((1 - x)*(1 - 6*x + x^2)). - Vaclav Kotesovec, Feb 14 2021 PROG (PARI) default(realprecision, 120); a(n) = round(sqrt(prod(j=1, n, prod(k=1, 2, 4*sin((2*j-1)*Pi/(2*n))^2+4*sin((2*k-1)*Pi/2)^2)))); CROSSREFS Column k=2 of A341533. Cf. A001541. Sequence in context: A019022 A079819 A238815 * A290357 A030112 A001555 Adjacent sequences: A341540 A341541 A341542 * A341544 A341545 A341546 KEYWORD nonn AUTHOR Seiichi Manyama, Feb 14 2021 STATUS approved

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Last modified December 1 21:09 EST 2022. Contains 358484 sequences. (Running on oeis4.)