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A121818
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Average of atomic weights of all isotopes of first n elements, rounded to nearest integer.
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2
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1, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 20, 21, 22, 23, 24, 25, 26, 27, 28, 30, 31, 32, 33, 34, 35, 36, 38, 39, 40, 41, 43, 44, 45, 46, 47, 49, 50, 51, 52, 53, 55, 56, 57, 58, 60, 61, 62, 63, 65, 66, 67, 69, 70, 71, 72, 74, 75, 76, 78, 79, 80, 81, 83, 84, 85
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OFFSET
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1,2
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COMMENTS
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This is poorly defined, even with the caveats of A007656, for the highest atomic numbers (with no stable isotopes) and the values given are with respect to Earth, as different planets presumably have slightly different isotopic ratios.
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LINKS
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EXAMPLE
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a(1) = round(1.0080/1) = 1 = mean atomic weight of hydrogen (protium + deuterium + tritium).
a(2) = round((1.0080+4.003)/2) = round(5.011/2) = round(2.5055) = 3.
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MATHEMATICA
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Needs["Miscellaneous`ChemicalElements`"]
Table[ Round[ Sum[ AtomicWeight(AT)Elements[[i]], {i, n}]/n], {n, 111}] (* Robert G. Wilson v, Sep 02 2006 *)
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CROSSREFS
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KEYWORD
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nonn,fini,less
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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