A305996 Rectangular array, by antidiagonals; row n consists of the numbers R(n)/n, where R(n) is row n of the array at A305995.

1, 10, 1, 65, 34, 1, 130, 260, 2, 1, 260, 884, 5, 10, 1, 340, 1300, 10, 26, 10, 2, 1105, 3380, 20, 260, 340, 20, 1, 1972, 8840, 50, 5140, 650, 52, 2, 1, 2210, 31300, 65, 8840, 1565, 100, 5, 260, 1, 4420, 82948, 68, 21320, 5525, 520, 10, 514, 2, 2

Offset: 1

Author

Clark Kimberling, Jun 16 2018

Keywords

• nonn
• tabl

Examples

			Northwest corner:
  1  10   65  130   260    340   1105
  1  34  260  884  1300   3380   8840
  1   2    5   10    20     50     65
  1  10   26  260  5140   8840  21430
  1  10  340  650  1565   5525   6260
  2  30   52  100   520  10280  17680
  1   2    5   10    20     25     50
		

Crossrefs

Cf. A077610, A229994, A229996, A229997, A229998, A229998, A305995.

Programs

Mathematica

z = 3000; r[n_] := Select[Divisors[n], GCD[#, n/#] == 1 &]; k[n_] := Length[r[n]];
t[n_] := Table[r[n][[k[n] + 1 - i]]/r[n][[k[1] + i - 1]], {i, 1, k[n]}];
s = Table[Plus @@ t[n], {n, 1, z}];
a[n_] := If[IntegerQ[s[[n]]], 1, 0];
u = Table[a[n], {n, 1, z}]; (*A229996*)
d = Denominator[s]; row[n_] := Flatten[Position[d, n]] (*A305995 array*)
rr[n_] := row[n]/n;
TableForm[Table[rr[n], {n, 1, 100}]] (* A305996 array *)
r1[n_, k_] := rr[n][[k]];
Flatten[Table[r1[n - k + 1, k], {n, 5}, {k, n, 1, -1}]]  (* A305996 sequence *)