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 A127750 Row sums of inverse of number triangle A(n,k) = 1/(2n+1) if k <= n <= 2k, 0 otherwise. 3
 1, 3, 2, 5, 2, 4, 2, 7, 2, 4, 2, 6, 2, 4, 2, 9, 2, 4, 2, 6, 2, 4, 2, 8, 2, 4, 2, 6, 2, 4, 2, 11, 2, 4, 2, 6, 2, 4, 2, 8, 2, 4, 2, 6, 2, 4, 2, 10, 2, 4, 2, 6, 2, 4, 2, 8, 2, 4, 2, 6, 2, 4, 2, 13, 2, 4, 2, 6, 2, 4, 2, 8, 2, 4, 2, 6, 2, 4, 2, 10, 2, 4, 2, 6, 2, 4, 2, 8, 2, 4, 2, 6, 2, 4, 2, 12, 2, 4, 2, 6, 2, 4, 2, 8, 2, 4 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Row sums of A127749. Conjecture: a(n) mod 2 gives Fredholm-Rueppel sequence A036987. The conjecture is true at least up to n=2048. - Antti Karttunen, Sep 29 2018 LINKS Antti Karttunen, Table of n, a(n) for n = 0..2048 MATHEMATICA A[n_, k_] := If[k <= n <= 2k, 1/(2n+1), 0]; Total /@ Inverse[Array[A, {128, 128}, {0, 0}]] (* Jean-François Alcover, Feb 10 2021 *) PROG (PARI) up_to = 128; A127750aux(n, k) = if(k<=n, if(n<=(2*k), 1/(n+n+1), 0), 0); A127750list(up_to) = { my(m1=matrix(up_to, up_to, n, k, A127750aux(n-1, k-1)), m2 = matsolve(m1, matid(up_to)), v = vector(up_to)); for(n=1, up_to, v[n] = vecsum(m2[n, ])); (v); }; v127750 = A127750list(1+up_to); A127750(n) = v127750[1+n]; \\ Antti Karttunen, Sep 29 2018 CROSSREFS Cf. A127749, A127752. Sequence in context: A231146 A287692 A208889 * A112528 A366687 A154421 Adjacent sequences: A127747 A127748 A127749 * A127751 A127752 A127753 KEYWORD nonn AUTHOR Paul Barry, Jan 28 2007 EXTENSIONS More terms from Antti Karttunen, Sep 29 2018 STATUS approved

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Last modified May 26 16:43 EDT 2024. Contains 372840 sequences. (Running on oeis4.)