OFFSET
1,1
LINKS
Wikipedia, Integer Triangle
EXAMPLE
6 is in the sequence since the integer-sided triangle [2,2,2] (with perimeter 6) has harmonic mean 3*2*2*2/(2*2+2*2+2*2) = 2 (an integer).
10 is in the sequence since the triangle [2,4,4] (with perimeter 10) has harmonic mean 3*2*4*4/(2*4+2*4+4*4) = 96/32 = 3 (an integer).
MATHEMATICA
Table[If[Sum[Sum[(1 - Ceiling[3*i*k*(n - i - k)/(i*k + k*(n - i - k) + i*(n - i - k))] + Floor[3*i*k*(n - i - k)/(i*k + k*(n - i - k) + i*(n - i - k))]) Sign[Floor[(i + k)/(n - i - k + 1)]], {i, k, Floor[(n - k)/2]}], {k, Floor[n/3]}] > 0, n, {}], {n, 100}] // Flatten
CROSSREFS
KEYWORD
nonn
AUTHOR
Wesley Ivan Hurt, Aug 14 2020
STATUS
approved