cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A296616 Lexicographically earliest sequence of distinct positive terms such that, for any n > 0, the binary expansion of a(n) * a(n + 1) starts with the binary expansion of n.

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%I A296616 #12 Dec 20 2017 12:13:33
%S A296616 1,2,4,3,6,7,14,8,16,9,18,5,10,11,21,12,22,13,23,27,24,28,26,29,53,31,
%T A296616 54,32,56,17,57,35,15,36,61,37,63,19,64,39,33,20,34,41,69,42,71,43,72,
%U A296616 44,73,45,74,46,38,47,77,48,78,49,79,25,40,51,81,52,82
%N A296616 Lexicographically earliest sequence of distinct positive terms such that, for any n > 0, the binary expansion of a(n) * a(n + 1) starts with the binary expansion of n.
%C A296616 It is likely that this sequence is a permutation of the natural numbers.
%C A296616 The lines visible in the scatterplot of the first terms seems to corresponds to set of indices n where the function f(n) = Sum_{k=1..n-1} (-1)^k * (A029837(1+a(k)*a(k+1)) - A029837(1+k)) has the same value; those lines can be partitioned into two groups, depending on the parity of n (see Links section).
%C A296616 This sequence has connections with A272679: here the binary expansion of a(n)*a(n+1) starts with that of n, there the binary expansion of a(n)^2 starts with that of n.
%H A296616 Rémy Sigrist, <a href="/A296616/b296616.txt">Table of n, a(n) for n = 1..10000</a>
%H A296616 Rémy Sigrist, <a href="/A296616/a296616.txt">C++ program for A296616</a>
%H A296616 Rémy Sigrist, <a href="/A296616/a296616.png">Colored scatterplot of the first 100000 terms</a> (where the color is function of Sum_{k=1..n-1} (-1)^k * (A029837(1+a(k)*a(k+1)) - A029837(1+k)))
%H A296616 Rémy Sigrist, <a href="/A296616/a296616_1.png">Colored scatterplot of the first 10000 terms</a> (where the color is function of the parity of n)
%e A296616 The first terms, alongside the binary representations of n and a(n) * a(n + 1), are:
%e A296616   n     a(n)    bin(n)    bin(a(n)*a(n+1))
%e A296616   --    ----    ------    ----------------
%e A296616    1       1         1            10
%e A296616    2       2        10          1000
%e A296616    3       4        11          1100
%e A296616    4       3       100         10010
%e A296616    5       6       101        101010
%e A296616    6       7       110       1100010
%e A296616    7      14       111       1110000
%e A296616    8       8      1000      10000000
%e A296616    9      16      1001      10010000
%e A296616   10       9      1010      10100010
%e A296616   11      18      1011       1011010
%e A296616   12       5      1100        110010
%e A296616   13      10      1101       1101110
%e A296616   14      11      1110      11100111
%e A296616   15      21      1111      11111100
%e A296616   16      12     10000     100001000
%e A296616   17      22     10001     100011110
%e A296616   18      13     10010     100101011
%e A296616   19      23     10011    1001101101
%e A296616   20      27     10100    1010001000
%o A296616 (C++) See Links section.
%Y A296616 Cf. A029837, A272679.
%K A296616 nonn,base
%O A296616 1,2
%A A296616 _Rémy Sigrist_, Dec 17 2017