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 A121818 Average of atomic weights of all isotopes of first n elements, rounded to nearest integer. 2
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS 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. LINKS EXAMPLE 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. MATHEMATICA (* first do *) Needs["Miscellaneous`ChemicalElements`"] (* then *) Table[ Round[ Sum[ AtomicWeight(AT)Elements[[i]], {i, n}]/n], {n, 111}] (* Robert G. Wilson v *) CROSSREFS Cf. A007656, A070217, A121291. Sequence in context: A062983 A081311 A053233 * A179005 A026505 A029674 Adjacent sequences:  A121815 A121816 A121817 * A121819 A121820 A121821 KEYWORD nonn AUTHOR Jonathan Vos Post, Aug 26 2006 EXTENSIONS More terms from Robert G. Wilson v, Sep 02 2006 Edited by N. J. A. Sloane, Sep 14 2006 STATUS approved

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