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A277905
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Irregular table: Each row n (n >= 0) lists in ascending order all A018819(n) numbers k for which A048675(k) = n.
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16
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1, 2, 3, 4, 6, 8, 5, 9, 12, 16, 10, 18, 24, 32, 15, 20, 27, 36, 48, 64, 30, 40, 54, 72, 96, 128, 7, 25, 45, 60, 80, 81, 108, 144, 192, 256, 14, 50, 90, 120, 160, 162, 216, 288, 384, 512, 21, 28, 75, 100, 135, 180, 240, 243, 320, 324, 432, 576, 768, 1024, 42, 56, 150, 200, 270, 360, 480, 486, 640, 648, 864, 1152, 1536, 2048, 35, 63, 84, 112, 125, 225, 300, 400
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OFFSET
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1,2
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COMMENTS
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Each row beginning with an odd number (rows with even index) is followed by a row of the same length, with the same terms, but multiplied by 2. See also comments in the Formula section of A018819.
Note that although the indexing of rows start from zero, the indexing of this sequence starts from 1, with a(1) = 1.
Also Heinz numbers of integer partitions whose binary rank is n, where the binary rank of a partition y is given by Sum_i 2^(y_i-1). For example, row n = 6 is 15, 20, 27, 36, 48, 64, corresponding to the partitions (3,2), (3,1,1), (2,2,2), (2,2,1,1), (2,1,1,1,1), (1,1,1,1,1,1). - Gus Wiseman, May 25 2024
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LINKS
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FORMULA
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a(1) = 1; for n > 1, if A277896(a(n-1)) > 0, then a(n) = A277896(a(n-1)), otherwise a(n) = A019565(A277903(n)). [A naive recurrence for a one-dimensional version.]
Other identities. For all n >= 1:
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EXAMPLE
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The irregular table begins as:
row terms
0 1;
1 2;
2 3, 4;
3 6, 8;
4 5, 9, 12, 16;
5 10, 18, 24, 32;
6 15, 20, 27, 36, 48, 64;
7 30, 40, 54, 72, 96, 128;
8 7, 25, 45, 60, 80, 81, 108, 144, 192, 256;
9 14, 50, 90, 120, 160, 162, 216, 288, 384, 512;
10 21, 28, 75, 100, 135, 180, 240, 243, 320, 324, 432, 576, 768, 1024;
11 42, 56, 150, 200, 270, 360, 480, 486, 640, 648, 864, 1152, 1536, 2048;
...
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MATHEMATICA
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prix[n_]:=If[n==1, {}, Flatten[Cases[FactorInteger[n], {p_, k_}:>Table[PrimePi[p], {k}]]]];
Table[Select[Range[0, 2^k], Total[2^(prix[#]-1)]==k&], {k, 0, 10}] (* Gus Wiseman, May 25 2024 *)
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PROG
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(Scheme)
(define (A277905bi row col) (let outloop ((k (A019565 row)) (col col)) (if (zero? col) k (let inloop ((j (+ 1 k))) (if (= (A048675 j) row) (outloop j (- col 1)) (inloop (+ 1 j))))))) ;; Very slow implementation.
;; Implementation based on a naive recurrence:
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CROSSREFS
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Cf. A019565 (the left edge, the only terms that are squarefree).
Row lengths are A018819 (number of partitions of binary rank n).
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KEYWORD
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nonn,tabf
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AUTHOR
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STATUS
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approved
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