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A309809
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a(n) is the concatenation of n and 2n+1.
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3
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13, 25, 37, 49, 511, 613, 715, 817, 919, 1021, 1123, 1225, 1327, 1429, 1531, 1633, 1735, 1837, 1939, 2041, 2143, 2245, 2347, 2449, 2551, 2653, 2755, 2857, 2959, 3061, 3163, 3265, 3367, 3469, 3571, 3673, 3775, 3877, 3979, 4081, 4183, 4285, 4387, 4489, 4591, 4693, 4795, 4897
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OFFSET
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1,1
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LINKS
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FORMULA
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a(n) = n*10^(ceiling(log_10(2*n+1))) + 2*n + 1.
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EXAMPLE
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a(3)=37 is the concatenation of 3 and 7.
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MAPLE
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seq(n*10^(ceil(log[10](2*n+1)))+2*n+1, n=1..100);
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MATHEMATICA
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Table[FromDigits[Join[IntegerDigits[n], IntegerDigits[2n+1]]], {n, 50}] (* Harvey P. Dale, Jan 30 2024 *)
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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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