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 A058038 Fibonacci(2n)*Fibonacci(2n+2). 14
 0, 3, 24, 168, 1155, 7920, 54288, 372099, 2550408, 17480760, 119814915, 821223648, 5628750624, 38580030723, 264431464440, 1812440220360, 12422650078083, 85146110326224, 583600122205488, 4000054745112195, 27416783093579880, 187917426909946968 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Partial sums of A033888, i.e., a(n) = Sum_{k=0..n} Fibonacci(4*k). - Vladeta Jovovic, Jun 09 2002 From Paul Weisenhorn, May 17 2009: (Start) a(n) is the solution of the 2 equations a(n)+1=A^2 and 5*a(n)+1=B^2 which are equivalent to the Pell equation (10*a(n)+3)^2-5*(A*B)^2=4. (End) Numbers a(n) such as a(n)+1 and 5*a(n)+1 are perfect squares. - Sture Sjöstedt, Nov 03 2011 REFERENCES A. T. Benjamin and J. J. Quinn, Proofs that really count: the art of combinatorial proof, M.A.A. 2003, id. 29. LINKS Harvey P. Dale, Table of n, a(n) for n = 0..1000 Index entries for linear recurrences with constant coefficients, signature (8,-8,1). FORMULA a(n) = -3/5 + (1/5*sqrt(5)+3/5)*(2*1/(7+3*sqrt(5)))^n/(7+3*sqrt(5)) + (1/5*sqrt(5)-3/5)*(-2*1/(-7+3*sqrt(5)))^n/(-7+3*sqrt(5)). Recurrence: a(n) = 8*a(n-1) - 8*a(n-2) + a(n-3). G.f.: 3*x/(1-7*x+x^2)/(1-x). - Vladeta Jovovic, Jun 09 2002 a(n) = A081068(n) - 1. a(n) is the next integer from ((3+sqrt(5))*((7+3*sqrt(5))/2)^(n-1)-6)/10. - Paul Weisenhorn, May 17 2009 a(n) = 7*a(n-1) - a(n-2) + 3, n>1. - Gary Detlefs, Dec 07 2010 a(n) = sum_{k=0..n} Fibonacci(4k). - Gary Detlefs, Dec 07 2010 a(n) = (Lucas(4n+2)-3)/5, where Lucas(n)= A000032(n). - Gary Detlefs, Dec 07 2010 a(n) = (1/5)*(Fibonacci(4n+4) - Fibonacci(4n)-3). - Gary Detlefs, Dec 08 2010 a(n) = 3*A092521(n). - R. J. Mathar, Nov 03 2011 a(0)=0, a(1)=3, a(2)=24, a(n) = 8*a(n-1) - 8*a(n-2) + a(n-3). - Harvey P. Dale, Jul 25 2013 a(n) = A001906(n)*A001906(n+1). - R. J. Mathar, Jul 09 2019 MAPLE fs4:=n->sum(fibonacci(4*k), k=0..n):seq(fs4(n), n=0..21); # Gary Detlefs, Dec 07 2010 MATHEMATICA Table[Fibonacci[2 n]*Fibonacci[2 n + 2], {n, 0, 100}] (* Vladimir Joseph Stephan Orlovsky, Jul 01 2011 *) Accumulate[Fibonacci[4*Range[0, 30]]] (* or *) LinearRecurrence[{8, -8, 1}, {0, 3, 24}, 30] (* Harvey P. Dale, Jul 25 2013 *) PROG (MAGMA) [Fibonacci(2*n)*Fibonacci(2*n+2): n in [0..30]]; // Vincenzo Librandi, Apr 18 2011 (PARI) a(n)=fibonacci(2*n)*fibonacci(2*n+2) \\ Charles R Greathouse IV, Jul 02 2013 CROSSREFS Cf. A033888, A004187. Bisection of A059929, A064831 and A080097. Related to sum of fibonacci(kn) over n; cf. A000071, A099919, A027941, A138134, A053606. Sequence in context: A289795 A094432 A104527 * A089697 A120741 A292293 Adjacent sequences:  A058035 A058036 A058037 * A058039 A058040 A058041 KEYWORD nonn,easy AUTHOR N. J. A. Sloane, Jun 09 2002 STATUS approved

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Last modified February 22 10:54 EST 2020. Contains 332135 sequences. (Running on oeis4.)