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A273475
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The successive numbers of digits between two "7"s in the sequence are given by the sequence itself.
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0
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0, 1, 2, 3, 4, 5, 6, 7, 70, 71, 8, 72, 9, 17, 10, 11, 73, 12, 13, 74, 14, 15, 27, 16, 18, 19, 37, 20, 21, 22, 23, 24, 25, 26, 28, 29, 30, 31, 32, 33, 34, 35, 36, 38, 39, 40, 41, 42, 43, 44, 45, 46, 48, 49, 50, 51, 52, 53, 54, 55, 56, 58, 75, 59, 60, 61, 62, 63, 64, 65, 66, 68, 69, 80, 81, 82, 83, 84, 85, 86, 88, 89, 90, 91, 92, 93, 94, 95, 96, 98, 99, 100, 101, 102, 103, 107, 104, 105, 117, 106, 108, 109, 110, 111, 112, 113, 114, 115, 116, 118, 119, 120, 121, 122, 123, 124, 125, 126, 128, 129, 130, 131, 132, 76, 133, 134, 127, 135, 136, 138, 139, 140, 137, 141, 142, 143, 47, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 158, 159, 160, 161
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OFFSET
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1,3
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COMMENTS
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This is the lexicographically first such sequence, starting with a(1)=0, that is always extended with the smallest integer not already present in the sequence and not leading to a contradiction.
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LINKS
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EXAMPLE
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There are 0 digits between the first two "7" of the sequence [0,1,2,3,4,5,6,7,70]; then there is 1 digit between the next pair of "7": [70,71]; then there are 2 digits between the next pair of "7": [71,8,72]; then there are 3 digits between the next pair of "7": [72,9,17]; then there are 4 digits between the next pair of "7": [17,10,11,73,]; then there are 5 digits between the next pair of "7": [73,12,13,74]; then there are 6 digits between the next pair of "7": [74,14,15,27], etc. The quantities 0, 1, 2, 3, 4, 5, 6,... rebuild the starting sequence. The next "gap" will contain 7 digits and the next one 70.
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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STATUS
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approved
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