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A283208
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Minimal exponent integer sequence associated with Vietoris sequence.
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1
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0, 2, 3, 6, 7, 9, 10, 14, 15, 17, 18, 21, 22, 24, 25, 30, 31, 33, 34, 37, 38, 40, 41, 45, 46, 48, 49, 52, 53, 55, 56, 62, 63, 65, 66, 69, 70, 72, 73, 77, 78, 80, 81, 84, 85, 87, 88, 93, 94, 96, 97, 100, 101, 103, 104, 108, 109, 111, 112, 115, 116, 118, 119
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OFFSET
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0,2
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COMMENTS
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a(n) is the least nonnegative integer such that 2^a(n) (2n+1)/(n+1) c(2n) is a nonnegative integer, where c(2n) = c(2n-1) = Pochhammer(1/2,n)/(n!) used in [Vietoris, Askey & Steinig, Ruscheweyh & Salinas] and named Vietoris sequence in [Cação et al.]. Also c(n) = A001405(n)/A000079(n).
Also 2^a(n) is the denominator of 2^(-2n)*A001700(n).
Sum_{k = -1..2} (-1)^ceiling(k/2 + 1) * a(4*n + k) = 6, for n >= 1.
Sum_{k = 1..4} (-1)^ceiling((k-1 mod 3)/3) * a(2*n + k) = 0, for n >= 0. (End)
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REFERENCES
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L. Vietoris. Über das Vorzeichen gewisser trigonometrischer Summen. Sitzungsber. Österr. Akad. Wiss., 167 (1958), 125-135.
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LINKS
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FORMULA
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a(n) = n + Sum_{j=1..k} floor((n+1)/(2^j)) where k = floor(log_2(n+1)) = A000523(1+n).
a(n+4) = a(n) + 6 + b(n), where b(n) = min(k, floor((n+5)/4 mod 2^k) = 1), for n >= 0.
a(n+4) = a(n) + 6 + A001511(ceiling((n+2)/4)), for n >= 0.
G.f.: ((2*x + x^2 + 3*x^3 + x^4)/(1 - x) + Sum_{k >= 0} (Sum_{i = 0..3} x^(8*2^k-1+i))/(1 - x^(8*2^k)))/(1 - x^4). (End)
a(n) = n + log_2((n+1)!-((n+1)! AND (n+1)!-1)) (empirical). - Gary Detlefs, Apr 29 2019 [True: equivalent to a(n) = n + A011371(n+1), which is equivalent to the top formula here. - Andrey Zabolotskiy, Mar 26 2021]
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EXAMPLE
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For n=3, a(3)=6 and 2^a(n)(2n+1)/(n+1) c(2n) = (2^6)*7/4*c(6) = 64*35/64 = 35.
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MATHEMATICA
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a[n_]:=n+Sum[Floor[(n+1)/(2^j)], {j, 1, Log2[n+1]}]
(* or *)
a[n_]:=Log2@Denominator[Binomial[2 n + 1, n+1] 2^(-2 n)]
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PROG
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(PARI) for(n=0, 62, print1(n + sum(j=1, logint(n + 1, 2), floor((n+1)/(2^j))), ", ")) \\ Indranil Ghosh, Mar 10 2017
(R)
soma <- n
for (i in c(1:ceiling(log2(n+1)))){soma <- soma + floor((n+1)/2^i)}
(Python)
def A283208(n): return n+sum((n+1)//(1<<j) for j in range(1, (n+1).bit_length()+2)) # Chai Wah Wu, Jul 16 2022
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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