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A140875
Triangle read by rows: T(n,m) = gcd(n,m+2) - 2*gcd(n,m+1) - gcd(n,m), with diagonal and subdiagonal removed.
0
-2, -4, 0, -4, -4, 0, -6, -2, -2, 2, -6, -2, -6, -6, 2, -8, -2, -2, -2, -2, 4, -8, -4, 0, -8, -4, -4, 4, -10, 0, -6, -4, 0, -6, -4, 6, -10, -4, -2, 0, -10, -8, -2, -4, 6, -12, -2, -2, -2, -2, -2, -2, -2, -2, 8, -12, -2, -4, -10, 0, -12, -4, -6, -8, -6, 8, -14, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, 10
OFFSET
1,1
EXAMPLE
{ -2},
{ -4, 0},
{ -4, -4, 0},
{ -6, -2, -2, 2},
{ -6, -2, -6, -6, 2},
{ -8, -2, -2, -2, -2, 4},
{ -8, -4, 0, -8, -4, -4, 4},
{-10, 0, -6, -4, 0, -6, -4, 6},
{-10, -4, -2, 0, -10, -8, -2, -4, 6}
MATHEMATICA
G[n_, m_] := GCD[n, m]
D2[n_, m_] := If[m + 2 <= n, G[n, m + 2] - 2*G[n, m + 1] - G[n, m], {} ];
a = Table[Flatten[Table[D2[n, m], {m, 0, n}]], {n, 0, 10}]; Flatten[a]
CROSSREFS
Cf. A109004.
Sequence in context: A134352 A152648 A327898 * A364315 A115368 A086932
KEYWORD
tabl,sign,easy,less
AUTHOR
EXTENSIONS
Definition corrected and more terms from Georg Fischer, Jun 08 2023
STATUS
approved