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 A065435 a(3) = 2, a(4) = 3; for n > 4, a(n) = {a(n-2)}+{a(n-1)}, where {a} means largest prime <= a. 2
 2, 3, 5, 8, 12, 18, 28, 40, 60, 96, 148, 228, 366, 586, 936, 1506, 2428, 3922, 6342, 10256, 16590, 26826, 43394, 70212, 113598, 183798, 297388, 481174, 778548, 1259712, 2038242, 3297918, 5336130, 8634042, 13970112, 22604076, 36574162 (list; graph; refs; listen; history; text; internal format)
 OFFSET 3,1 LINKS Harry J. Smith, Table of n, a(n) for n = 3..300 FORMULA a(n) = A007917(a(n-2)) + A007917(a(n-1)). - Jonathan Vos Post, Jul 10 2008 EXAMPLE a(9) = 28 because 11+17 = 28 and 11 largest prime <= a(7) = 12 and 17 is largest prime <= a(8) = 18 MATHEMATICA PrevPrim[n_] := Block[ {k = n}, While[ !PrimeQ[k], k-- ]; Return[k]]; a[3] = 2; a[4] = 3; a[n_] := a[n] = PrevPrim[ a[n - 1]] + PrevPrim[ a[n - 2]]; Table[ a[n], {n, 3, 45} ] np[n_]:=If[PrimeQ[n], n, NextPrime[n, -1]]; Transpose[NestList[{Last[#], np[Last[#]]+np[First[#]]}&, {2, 3}, 40]][[1]] (* Harvey P. Dale, Oct 01 2011 *) PROG (PARI) for (n=3, 300, if (n>4, a=precprime(a2) + precprime(a1); a2=a1; a1=a, if (n==4, a=a1=3, a=a2=2)); write("b065435.txt", n, " ", a) ) \\ Harry J. Smith, Oct 18 2009 (Haskell) a065435 n = a065435_list !! (n-3) a065435_list = 2 : 3 : zipWith (+) xs (tail xs) where xs = map (a007917 . fromInteger) a065435_list -- Reinhard Zumkeller, Aug 10 2012 CROSSREFS Cf. A055500, A000040, A000045, A007917, A055500. Sequence in context: A061419 A130732 A018135 * A301750 A086676 A055804 Adjacent sequences: A065432 A065433 A065434 * A065436 A065437 A065438 KEYWORD nonn,easy,nice AUTHOR Bodo Zinser, Nov 17 2001 EXTENSIONS More terms from Robert G. Wilson v, Nov 19 2001 Definition corrected by Harry J. Smith, Oct 18 2009 STATUS approved

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Last modified April 12 17:42 EDT 2024. Contains 371635 sequences. (Running on oeis4.)