OFFSET
1,7
LINKS
Robert Israel, Table of n, a(n) for n = 1..2500
Wikipedia, Integer Triangle
FORMULA
MAPLE
N:= 100: # for a(1)..a(N)
A:= Vector(N):
for a from 1 to floor(N/3) do
for b from a to floor((N-a)/2) do
if igcd(a, b) = 1 then
C:= select(c -> igcd(c, a*b) <> 1, [$b .. min(a+b-1, N-a-b)])+~ (a+b)
else C:= [$b .. min(a+b-1, N-a-b)] +~ (a+b)
fi;
A[C]:= A[C] +~ 1
od od:
convert(A, list); # Robert Israel, Oct 03 2023
MATHEMATICA
Table[Sum[Sum[(1 - KroneckerDelta[GCD[i, k]*GCD[i, n - i - k]*GCD[k, n - i - k], 1])*Sign[Floor[(i + k)/(n - i - k + 1)]], {i, k, Floor[(n - k)/2]}], {k, Floor[n/3]}], {n, 100}]
CROSSREFS
KEYWORD
nonn,look
AUTHOR
Wesley Ivan Hurt, May 19 2019
STATUS
approved