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 A072703 Indices of Fibonacci numbers whose last digit is 5. 2
 5, 10, 20, 25, 35, 40, 50, 55, 65, 70, 80, 85, 95, 100, 110, 115, 125, 130, 140, 145, 155, 160, 170, 175, 185, 190, 200, 205, 215, 220, 230, 235, 245, 250, 260, 265, 275, 280, 290, 295, 305, 310, 320, 325, 335, 340, 350, 355, 365, 370, 380 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Sequence contains numbers of the forms 5 + 60*k, 10 + 60*k, 20 + 60*k, 25 + 60*k, 35 + 60*k, 40 + 60*k, 50 + 60*k, 55 + 60*k, where k>=0. LINKS Index entries for linear recurrences with constant coefficients, signature (1,1,-1). FORMULA a(n) = 15*(n-1)-a(n-1), with a(1)=5. - Vincenzo Librandi, Aug 08 2010] a(1)=5, a(2)=10, a(3)=20, a(n)=a(n-1)+a(n-2)-a(n-3). - Harvey P. Dale, May 15 2011 a(n) = -(5/4)*(3+(-1)^n-6*n). - Harvey P. Dale, May 15 2011 G.f.: 5*x*(x^2+x+1) / ((x-1)^2*(x+1)). - Colin Barker, Jun 16 2013 MATHEMATICA Flatten[Position[Fibonacci[Range[400]], _?(Last[IntegerDigits[#]]==5&)]] (* or *) LinearRecurrence[{1, 1, -1}, {5, 10, 20}, 60] (* or *) Table[-(5/4) (3+(-1)^n-6 n), {n, 60}] (* Harvey P. Dale, May 15 2011 *) CROSSREFS Cf. A000045, A003893. Sequence in context: A062052 A245387 A115799 * A086761 A045191 A065958 Adjacent sequences:  A072700 A072701 A072702 * A072704 A072705 A072706 KEYWORD nonn,base,easy AUTHOR Benoit Cloitre, Aug 07 2002 EXTENSIONS Edited by M. F. Hasler, Oct 08 2014 STATUS approved

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Last modified September 18 23:16 EDT 2021. Contains 347548 sequences. (Running on oeis4.)