OFFSET
1,2
COMMENTS
It has been proved that three consecutive Ulam numbers U(n) for n > 1 satisfy the triangle inequality. See Wikipedia link below.
LINKS
Alois P. Heinz, Table of n, a(n) for n = 1..1000
Wikipedia, Ulam number.
FORMULA
Given a triangle with sides a, b and c, the area A = sqrt(s(s-a)(s-b)(s-c)) where s = (a+b+c)/2.
EXAMPLE
a(2) = 2 because the triangle with sides (2, 3, 4) has area 3*sqrt(15)/4 = 2.9047...
MATHEMATICA
lst1 = ReadList["https://oeis.org/A002858/b002858.txt", {Number, Number}]; lst={}; Do[{a, b, c}={lst1[[n]][[2]], lst1[[n+1]][[2]], lst1[[n+2]][[2]]}; s = (a+b+c)/2; A=Sqrt[s(s-a)(s-b)(s-c)]; AppendTo[lst, Floor@A], {n, 1, 50}]; lst
CROSSREFS
KEYWORD
nonn
AUTHOR
Frank M Jackson, May 01 2020
STATUS
approved