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 A005707 a(1) = a(2) = a(3) = a(4) = 1, a(n) = a(a(n-1))+a(n-a(n-1)) for n >= 5. (Formerly M0251) 3
 1, 1, 1, 1, 2, 2, 3, 3, 3, 4, 4, 4, 4, 5, 6, 6, 6, 6, 6, 7, 8, 8, 9, 9, 9, 9, 9, 9, 10, 11, 11, 12, 12, 12, 13, 13, 13, 13, 13, 13, 13, 14, 15, 16, 16, 17, 17, 17, 18, 18, 18, 18, 19, 19, 19, 19, 19, 19, 19, 19, 20, 21, 22, 22, 23, 24, 24, 25, 25, 25, 26, 26, 26, 26, 27, 27, 27, 27, 27 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,5 COMMENTS It is known that a(n)-a(n-1)=0 or 1 (see the 1991 Monthly reference). - Emeric Deutsch, Jun 06 2005 REFERENCES N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS T. D. Noe, Table of n, a(n) for n=1..1000 D. Kleitman, Solution to Problem E3274, Amer. Math. Monthly, 98 (1991), 958-959. R. K. Guy and N. J. A. Sloane, Correspondence, 1988. D. Newman, Problem E3274, Amer. Math. Monthly, 95 (1988), 555. MAPLE a[1]:=1: a[2]:=1: a[3]:=1: a[4]:=1: for n from 5 to 100 do a[n]:=a[a[n-1]]+a[n-a[n-1]] od: seq(a[n], n=1..100); # Emeric Deutsch, Jun 06 2005 MATHEMATICA a[1]=a[2]=a[3]=a[4]=1; a[n_]:=a[n]=a[a[n-1]]+a[n-a[n-1]]; Table[a[i], {i, 80}] (* Harvey P. Dale, Jan 22 2013 *) PROG (Haskell) a005707 n = a005707_list !! (n-1) a005707_list = 1 : 1 : 1 : 1 : h 5 1 where    h x y = z : h (x + 1) z where z = a005707 y + a005707 (x - y) -- Reinhard Zumkeller, Jul 20 2012 CROSSREFS Cf. A004001, A005350. Cf. A005185. Sequence in context: A132073 A087817 A091497 * A087828 A330779 A110867 Adjacent sequences:  A005704 A005705 A005706 * A005708 A005709 A005710 KEYWORD nonn,easy,nice AUTHOR EXTENSIONS More terms from Emeric Deutsch, Jun 06 2005 STATUS approved

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Last modified August 4 08:25 EDT 2020. Contains 336201 sequences. (Running on oeis4.)