A318998 - OEIS

%I #17 Apr 15 2023 15:15:29

%S 1,2,1,1,1,2,2,2,2,1,3,1,3,1,3,1,3,1,3,0,5,1,3,1,3,1,3,2,5,1,4,1,3,1,

%T 3,0,3,1,3,0,4,1,4,1,4,0,4,1,4,1,6,1,4,1,3,2,4,1,5,1,4,0,4,1,4,2,3,1,

%U 3,1,4,1,4,1,5,1,3,1,5,1,3,2,7,1,2,2,2

%N Number of stable nuclides with neutron number n.

%C Radioactive nuclides with a half-life of 700 million years or greater (i.e., half-life longer than or equal to that of uranium-235) are included.

%C The last known term is a(177) = 0.

%C Sum_{n=0..177} a(n) = 286, which is the number of known stable nuclides.

%C For n <= 126, a(n) = 0 for n = 19, 35, 39, 45, 61, 89, 115, 123.

%C The total number of stable nuclides with an even neutron number is 220, while for odd neutron number it's 66.

%C The number of even numbers k such that a(k) = 1, 2, 3, 4, 5, 6, 7 are 5, 6, 28, 19, 6, 1, 1. There are 46 odd numbers such that a(k) = 1 and only 10 such that a(k) = 2.

%H Jianing Song, <a href="/A318998/b318998.txt">Table of n, a(n) for n = 0..177</a>

%H Wikipedia, <a href="https://en.wikipedia.org/wiki/Table_of_nuclides_%28segmented,_narrow%29">Table of nuclides</a>.

%H Wikipedia, <a href="https://en.wikipedia.org/wiki/Neutron_number">Neutron number</a>.

%H Wikipedia, <a href="https://en.wikipedia.org/wiki/Isotone">Isotone</a>.

%e Stable nuclides with neutron number n:

%e n = 20: sulfur-36, chlorine-37, argon-38, potassium-39, calcium-40;

%e n = 50: krypton-86, rubidium-87, strontium-88, yttrium-89, zirconium-90, molybdenum-92;

%e n = 85: neodymium-145, samarium-147.

%Y Cf. A179301 (proton number), A318997 (mass number), A318999 (neutron excess).

%K nonn

%O 0,2

%A _Jianing Song_, Sep 07 2018