%I A121291
%S A121291 1,5,12,21,31,43,57,73,92,112,135,160,187,215,246,278,318,353,392,432,
%T A121291 477,525,576,628,683,739,798,857,920,986,1055,1128,1203
%N A121291 Rounded partial sum of atomic weights of first n elements.
%e A121291 a(1) = round(1.0080) = 1 = mean atomic weight of hydrogen (protium + 
               deuterium + tritium).
%e A121291 a(2) = round (1.0080+4.003) = round(5.011) = 5 (heium 4 and rarer helium 
               3).
%Y A121291 Cf. A007656, A070217.
%Y A121291 Sequence in context: A047077 A086570 A063559 this_sequence A097984 A028347 
               A038794
%Y A121291 Adjacent sequences: A121288 A121289 A121290 this_sequence A121292 A121293 
               A121294
%K A121291 nonn
%O A121291 1,2
%A A121291 Jonathan Vos Post (jvospost3(AT)gmail.com), Aug 24 2006