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 A014980 a(n+1) = floor(a(n)/2) * ceiling(a(n)/2), a(0) = 5. 4
 5, 6, 9, 20, 100, 2500, 1562500, 610351562500, 93132257461547851562500, 2168404344971008868014905601739883422851562500, 1175494350822287507968736537222245677818665556772087521508751706278417259454727172851562500 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS A194079(n) gives number of digits of a(n). LINKS Table of n, a(n) for n=0..10. FORMULA a(0) = 5; a(k+1) = floor(a(k)/2) * ceiling(a(k)/2). a(n+1) = A002620(a(n)), a(0) = 5. - Reinhard Zumkeller, Oct 12 2011 EXAMPLE 6 = 2*3; 9 = 3*3; 20 = 4*5; ... MATHEMATICA a=5; a=Table[a=Ceiling[a/2]*Floor[a/2], {n, 0, 10}] (* Vladimir Joseph Stephan Orlovsky, Apr 13 2010 *) NestList[Floor[#/2]Ceiling[#/2]&, 5, 10] (* Harvey P. Dale, Jul 10 2012 *) PROG (Haskell) a014980 n = a014980_list !! n a014980_list = iterate a002620 5 -- Reinhard Zumkeller, Oct 12 2011 (Python) from itertools import accumulate def f(an, _): return (an//2)*((an+1)//2) print(list(accumulate([5]*11, f))) # Michael S. Branicky, May 06 2021 CROSSREFS Cf. A002620, A194079. Sequence in context: A322959 A154311 A279702 * A066901 A273039 A019125 Adjacent sequences: A014977 A014978 A014979 * A014981 A014982 A014983 KEYWORD nonn,nice,easy AUTHOR Colin Sandon (sandon(AT)together.net) EXTENSIONS More terms from James A. Sellers, Feb 05 2000 STATUS approved

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Last modified September 24 09:38 EDT 2023. Contains 365579 sequences. (Running on oeis4.)