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 A265735 Integers in the interval [Pi*k - 1/k, Pi*k + 1/k] for some k > 0. 2
 3, 4, 6, 19, 22, 44, 66, 88, 333, 355, 710, 1065, 1420, 1775, 2130, 2485, 2840, 3195, 3550, 3905, 4260, 4615, 4970, 5325, 5680, 6035, 103993, 104348, 208341, 312689, 521030, 833719, 1146408, 2292816, 4272943, 5419351, 10838702, 16258053, 80143857, 85563208 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Conjecture: the sequence is infinite. See the reference for a similar problem with Fibonacci numbers. For k > 1, the interval [Pi*k - 1/k, Pi*k + 1/k] contains exactly one integer. The corresponding integers k are 1, 2, 6, 7, 14, 21, 28,...(see A265739). We observe two properties: (1) a(n) = m*a(n-m+1) for some n, m=2,3,4. Examples: m = 2 => a(7)=2*a(6), a(11)=2*a(10), a(15)=2*a(14), a(20)=2*a(19), a(25)=2*a(24), a(30)=2*a(29),... m = 3 => a(16)=3*a(14), a(21)=3*a(19), a(26)=3*a(24), a(31)=3*a(29),... m = 4 => a(4)=4*a(1), a(32)=4*a(29), … But, for m=5, the formula (1) is not valid. We find a(13)=5*a(9), a(18)=5*a(10), a(23)=5*a(11),… (2) a(n+2) = a(n) + a(n+1) for n = 4, 9, 26, 27, 28, 29, 35,.. LINKS Takao Komatsu, The interval associated with a Fibonacci number, The Fibonacci Quarterly, Volume 41, Number 1, February 2003. EXAMPLE For k=1 there exists two integers a(1)=3 and a(2)=4 in the interval [1*Pi -1/1, 1*Pi + 1/1] = [2.14159...,4.14159...]; for k=2, the number a(3)=6 is in the interval [2*Pi-1/2, 2*Pi+1/2] = [5.783185..., 6.783185...]; for k=6, the number a(4)= 19 is in the interval [6*Pi-1/6, 6*Pi+1/6] = [18.682889..., 19.016223...]. MAPLE *** the program gives the interval [a, b], a(n) and k *** nn:=10^9: for n from 1 to nn do: x1:=evalhf(Pi*n-1/n):y1:=evalhf(Pi*n+1/n): x:=floor(x1):y:=floor(y1): for j from x+1 to y do: printf("%g %g %d %d\n", x1, y1, j, n): od: od: CROSSREFS Cf. A000796, A265739. Sequence in context: A136242 A066732 A304679 * A038520 A294990 A081888 Adjacent sequences:  A265732 A265733 A265734 * A265736 A265737 A265738 KEYWORD nonn AUTHOR Michel Lagneau, Dec 15 2015 STATUS approved

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Last modified December 5 15:11 EST 2019. Contains 329753 sequences. (Running on oeis4.)