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 A049920 a(n) = a(1) + a(2) + ... + a(n-1) - a(m) for n >= 4, where m = 2*n - 3 - 2^(p+1) and p is the unique integer such that 2^p < n-1 <= 2^(p+1), with a(1) = 1, a(2) = 3, and a(3) = 2. 2
 1, 3, 2, 5, 9, 19, 37, 67, 106, 248, 495, 983, 1938, 3807, 7225, 13007, 20727, 48678, 97355, 194703, 389378, 778687, 1556985, 3112527, 6219767, 12426032, 24775436, 49258849, 97350091, 190037400, 361519131, 650463607, 1036758174 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS The number m in the definition of the sequence equals 2*n - 3 - x, where x is the smallest power of 2 >= n-1. It turns out that m =  A006257(n-2), where the sequence b(n) = A006257(n) satisfies b(2*n) = 2*b(n) - 1 and b(2*n + 1) = 2*b(n) + 1, and it is related to the so-called Josephus's problem. - Petros Hadjicostas, Sep 25 2019 LINKS Robert Israel, Table of n, a(n) for n = 1..3323 FORMULA a(n) = -a(A006257(n-2)) + Sum_{i = 1..n-1} a(i) for n >= 4 with a(1) = 1, a(2) = 3, and a(3) = 2. EXAMPLE From Petros Hadjicostas, Sep 25 2019: (Start) a(4) = -a(A006257(4-2)) + a(1) + a(2) + a(3) = -a(1) + a(1) + a(2) + a(3) = 5. a(5) = -a(A006257(5-2)) + a(1) + a(2) + a(3) + a(4) = -a(3) + a(1) + a(2) + a(3) + a(4) = 9. a(6) = -a(A006257(6-2)) + a(1) + a(2) + a(3) + a(4) + a(5) = 19. a(7) = -a(A006257(7-2)) + a(1) + a(2) + a(3) + a(4) + a(5) + a(6) = 37. (End) MAPLE A:= 1: A:= 3: A:= 2: for n from 4 to 100 do   q:= ceil(log(n-1));   m:= 2*n-3-2^q;   A[n]:= add(A[i], i=1..n-1)-A[m]; od: seq(A[i], i=1..100); # Robert Israel, Feb 27 2017 CROSSREFS Cf. A006257, A049939, A049960, A049964, A049979. Sequence in context: A249906 A258930 A002797 * A257981 A128914 A050063 Adjacent sequences:  A049917 A049918 A049919 * A049921 A049922 A049923 KEYWORD nonn AUTHOR EXTENSIONS Name edited by Petros Hadjicostas, Sep 25 2019 STATUS approved

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Last modified September 29 05:01 EDT 2020. Contains 337420 sequences. (Running on oeis4.)