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 A326783 BII-numbers of uniform set-systems. 6
 0, 1, 2, 3, 4, 8, 9, 10, 11, 16, 20, 32, 36, 48, 52, 64, 128, 129, 130, 131, 136, 137, 138, 139, 256, 260, 272, 276, 288, 292, 304, 308, 512, 516, 528, 532, 544, 548, 560, 564, 768, 772, 784, 788, 800, 804, 816, 820, 1024, 1088, 2048, 2052, 2064, 2068, 2080 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS A binary index of n is any position of a 1 in its reversed binary expansion. The binary indices of n are row n of A048793. We define the set-system with BII-number n to be obtained by taking the binary indices of each binary index of n. A set-system is uniform if all edges have the same size. Alternatively, these are numbers whose binary indices all have the same binary weight, where the binary weight of a nonnegative integer is the numbers of 1's in its binary digits. LINKS EXAMPLE The sequence of all uniform set-systems together with their BII-numbers begins:     0: {}     1: {{1}}     2: {{2}}     3: {{1},{2}}     4: {{1,2}}     8: {{3}}     9: {{1},{3}}    10: {{2},{3}}    11: {{1},{2},{3}}    16: {{1,3}}    20: {{1,2},{1,3}}    32: {{2,3}}    36: {{1,2},{2,3}}    48: {{1,3},{2,3}}    52: {{1,2},{1,3},{2,3}}    64: {{1,2,3}}   128: {{4}}   129: {{1},{4}}   130: {{2},{4}}   131: {{1},{2},{4}} MATHEMATICA bpe[n_]:=Join@@Position[Reverse[IntegerDigits[n, 2]], 1]; Select[Range[0, 100], SameQ@@Length/@bpe/@bpe[#]&] CROSSREFS Cf. A000120, A029931, A048793, A070939, A047966, A306017, A306021, A319269, A320324, A326031, A326784 (regular), A326785 (uniform regular), A326788. Sequence in context: A047338 A069811 A004826 * A326785 A327080 A291621 Adjacent sequences:  A326780 A326781 A326782 * A326784 A326785 A326786 KEYWORD nonn AUTHOR Gus Wiseman, Jul 25 2019 STATUS approved

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Last modified April 13 03:43 EDT 2021. Contains 342934 sequences. (Running on oeis4.)