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 A007751 Even bisection of A007750. 3
 0, 7, 120, 1921, 30624, 488071, 7778520, 123968257, 1975713600, 31487449351, 501823476024, 7997688167041, 127461187196640, 2031381306979207, 32374639724470680, 515962854284551681, 8223031028828356224 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS G. C. Greubel, Table of n, a(n) for n = 0..825 K. R. S. Sastry, Problem 533 The College Mathematics Journal, 25, issue 4, 1994, p. 334. K. R. S. Sastry, Square Products of Sums of Squares The College Mathematics Journal, 26, issue 4, 1995, p. 333. Index entries for linear recurrences with constant coefficients, signature (17,-17,1). FORMULA G.f.: x*(7 + x)/((1-x)*(1-16*x+x^2)). a(n) = 16*a(n-1) - a(n-2) + 8. a(n) = -4/7 + (2/7)*( (8-3*sqrt(7))^n + (8+3*sqrt(7))^n + (sqrt(7)/14)*( (8+3*sqrt(7))^n - (8-3*sqrt(7))^n ), with n>=0 - Paolo P. Lava, Jun 19 2008 a(n) = (4*ChebyshevU(n,8) - 11*ChebyshevU(n-1,8) -4)/7. - G. C. Greubel, Feb 10 2020 E.g.f.: (cosh(x) + sinh(x))*(-4 + (cosh(7*x) + sinh(7*x))*(4*cosh(3*sqrt(7)*x) + sqrt(7)*sinh(3*sqrt(7)*x)))/7. - Stefano Spezia, Feb 20 2020 MAPLE seq(simplify((4*ChebyshevU(n, 8) -11*ChebyshevU(n-1, 8) -4)/7)), n = 0..30); # G. C. Greubel, Feb 10 2020 MATHEMATICA Table[(4*ChebyshevU[n, 8] -11*ChebyshevU[n-1, 8] -4)/7, {n, 0, 30}] (* G. C. Greubel, Feb 10 2020 *) PROG (PARI) a(n)=local(w); w=8+3*quadgen(28); imag(w^n)+4*(real(w^n)-1)/7 (PARI) vector(31, n, my(m=n-1); (4*polchebyshev(m, 2, 8) -11*polchebyshev(m-1, 2, 8) -4)/7 ) \\ G. C. Greubel, Feb 10 2020 (MAGMA) I:=[0, 7, 120]; [n le 3 select I[n] else 17*Self(n-1) -17*Self(n-2) +Self(n-3): n in [1..30]]; // G. C. Greubel, Feb 10 2020 (Sage) [(4*chebyshev_U(n, 8) -11*chebyshev_U(n-1, 8) -4)/7 for n in (0..30)] # G. C. Greubel, Feb 10 2020 (GAP) a:=[0, 7, 120];; for n in [4..30] do a[n]:=17*a[n-1]-17*a[n-2]+a[n-3]; od; a; # G. C. Greubel, Feb 10 2020 CROSSREFS Cf. A007750, A007752, A077412. Sequence in context: A092612 A263943 A302718 * A193785 A253276 A156955 Adjacent sequences:  A007748 A007749 A007750 * A007752 A007753 A007754 KEYWORD nonn AUTHOR John C. Hallyburton, Jr. (hallyb(AT)vmsdev.enet.dec.com) EXTENSIONS Edited by Michael Somos, Jul 27 2002 STATUS approved

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Last modified April 14 15:18 EDT 2021. Contains 342949 sequences. (Running on oeis4.)