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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

Table of n, a(n) for n=1..72.

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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Last modified August 22 22:22 EDT 2017. Contains 290952 sequences.