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A352696
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a(n) = k if the binary representation of k has a 1 (0) exactly where a 1 in the n-th row of A237048 occurs at an odd (even) position, reading from left to right.
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2
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1, 1, 2, 1, 2, 3, 2, 1, 5, 2, 2, 3, 2, 2, 11, 1, 2, 6, 2, 3, 10, 2, 2, 3, 5, 2, 10, 3, 2, 13, 2, 1, 10, 2, 11, 6, 2, 2, 10, 3, 2, 13, 2, 2, 45, 2, 2, 3, 5, 5, 10, 2, 2, 13, 10, 3, 10, 2, 2, 14, 2, 2, 43, 1, 10, 13, 2, 2, 10, 11, 2, 7, 2, 2, 44, 2, 11, 12, 2, 3, 21, 2, 2, 14, 10
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OFFSET
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1,3
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COMMENTS
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The phrase "symmetric representation of sigma(n)" is abbreviated below as SRS(n).
Every number in this sequence is a nondiving number and therefore in A061854. Number 22 with binary pattern 10110 is the smallest nondiving number in A061854, but not in this sequence since a number n with 5 odd divisors must have the form n = 2^m * p^4 for some prime p and some m>=0, and the pattern 10110 of odd/even positions of 1's in a row of A237048 requires 1's at positions 1 < 2^(m+1) < p < p^2 < 2^(m+1) * p <= row(n), a contradiction.
a(2^n) = 1 for all n>=0. The single part of SRS(2^n) has width 1, see A238443.
a(2^m * p) = 3 for odd primes p < 2^(m+1) with m >= 1. SRS(2^m * p) consists of a single part whose 2 subparts have sizes 2*T(n, 1) - 1 = 2^m * p - 1 and 2*T(n, p) - 1 = 2^m - p where T(n, k) = ceiling((n+1)/k -(k+1)/2), see A235791. The numbers 2^m * p are a subsequence of A174973 = A238443.
a(p^k) = A000975(k+1) for all odd primes p and k >= 0. Number a(p^k) in binary has k+1 digits with 1's and 0's alternating. SRS(p^k) has k+1 parts all of width 1 and of the symmetric sizes T(p^k, p^i) - T(p^k, 2*p^i) = (p^(k-i) + p^i)/2, for 0 <= i <= k. The numbers p^k are a subsequence of A174905, the odd primes p form the 1st column in the irregular triangle of A239929 and the numbers p^2 form the 1st column in the irregular triangle of A247687.
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LINKS
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EXAMPLE
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Sequence values for the first 4 powers of 3: {a(1), a(3), a(9), a(27)} = {1, 2, 5, 10} = {1, 10, 101, 1010}.
Table for a(1..16), a(27) and a(28) together with their lists of the base-2 representation, of the odd/even positions of 1's in the n-th row of A237048, and of the sizes of the parts in SRS(n):
1 1 {1} {1} {1}
2 1 {1} {1} {3}
3 2 {1,0} {1,1} {2,2}
4 1 {1} {1,0} {7}
5 2 {1,0} {1,1} {3,3}
6 3 {1,1} {1,0,1} {12}
7 2 {1,0} {1,1,0} {4,4}
8 1 {1} {1,0,0} {15}
9 5 {1,0,1} {1,1,1} {5,3,5}
10 2 {1,0} {1,0,0,1} {9,9}
11 2 {1,0} {1,1,0,0} {6,6}
12 3 {1,1} {1,0,1,0} {28}
13 2 {1,0} {1,1,0,0} {7,7}
14 2 {1,0} {1,0,0,1} {12,12}
15 11 {1,0,1,1} {1,1,1,0,1} {8,8,8}
16 1 {1} {1,0,0,0,0} {31}
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27 10 {1,0,1,0} {1,1,1,0,0,1} {14,6,6,14}
28 3 {1,1} {1,0,0,0,0,0,1} {56}
...
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MATHEMATICA
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(* function a237048[ ] is defined in A237048 *)
b237048[n_] := Fold[2#1+Mod[#2, 2]&, 0, Flatten[Position[a237048[n], 1]]]
a352696[n_] := Map[b237048, Range[n]]
a352696[85]
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CROSSREFS
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Cf. A000975, A061854, A174905, A174973, A235791, A237048, A237270, A237591, A237593, A238443, A239929, A247687, A352030.
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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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