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A265291 Decimal expansion of Sum_{n >= 1} (x - c(2n-1)), where c(n) = the n-th convergent to x = sqrt(2). 4

%I #13 Aug 23 2022 09:52:42

%S 4,2,8,8,6,0,3,3,8,0,6,8,0,9,5,9,8,3,0,0,2,1,1,1,3,6,7,6,1,3,2,7,2,3,

%T 0,7,2,3,9,6,0,1,7,6,5,1,2,5,6,0,8,2,7,4,6,6,8,3,0,2,9,6,0,2,2,3,0,5,

%U 6,9,3,1,3,7,0,6,6,5,3,5,8,8,2,6,1,4

%N Decimal expansion of Sum_{n >= 1} (x - c(2n-1)), where c(n) = the n-th convergent to x = sqrt(2).

%F From _Peter Bala_, Aug 20 2022: (Start)

%F Equals Sum_{n >= 1} (-1)^(n+1)/Pell(2*n), where Pell(n) = A000129(n).

%F Equals 2*sqrt(2)*Sum_{n >= 1} x^(n*(n+1)/2)/(x^n - 1), where x = 2^sqrt(2) - 3. (End)

%e sum = 0.4288603380680959830021113676132723...

%p x := 2*sqrt(2) - 3:

%p evalf(2*sqrt(2)*add( x^(n*(n+1)/2)/(x^n - 1), n = 1..16), 100); # _Peter Bala_, Aug 21 2022

%t x = Sqrt[2]; z = 600; c = Convergents[x, z];

%t s1 = Sum[x - c[[2 k - 1]], {k, 1, z/2}]; N[s1, 200]

%t s2 = Sum[c[[2 k]] - x, {k, 1, z/2}]; N[s2, 200]

%t N[s1 + s2, 200]

%t RealDigits[s1, 10, 120][[1]] (* A265291 *)

%t RealDigits[s2, 10, 120][[1]] (* A265292 *)

%t RealDigits[s1 + s2, 10, 120][[1]](* A265293 *)

%Y Cf. A000129, A001227, A002193, A265292, A265293, A265288 (guide).

%K nonn,cons

%O 0,1

%A _Clark Kimberling_, Dec 06 2015

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Last modified March 28 05:02 EDT 2024. Contains 371235 sequences. (Running on oeis4.)