OFFSET
1,2
COMMENTS
Every positive integer occurs exactly once, so that as a sequence, this is a permutation of the positive integers. The numbers in row n are divisible by n; see A305996 for the quotients.
EXAMPLE
Northwest corner:
1 10 65 130 260 340 1105
2 68 520 1768 2600 6760 17680
3 6 15 30 60 150 195
4 40 104 1040 20560 35360 85280
5 50 1700 3250 7825 27625 31300
12 120 312 600 3120 61680 106080
7 14 35 70 140 175 350
8 2080 4112 6560 32800 38048 52000
9 18 90 369 585 612 738
MATHEMATICA
t[n_] := Table[r[n][[k[n] + 1 - i]]/r[n][[k[1] + i - 1]], {i, 1, k[n]}];
s = Table[Total[t[n]], {n, 1, z}]; a[n_] := If[IntegerQ[s[[n]]], 1, 0];
d = Denominator[s];
row[n_] := Flatten[Position[d, n]]
TableForm[Table[row[n], {n, 1, 10}]] (* A305995 array *)
r1[n_, k_] := row[n][[k]]; zz = 10;
Flatten[Table[r1[n - k + 1, k], {n, zz}, {k, n, 1, -1}]] (* A305995 sequence *)
CROSSREFS
KEYWORD
nonn,tabl
AUTHOR
Clark Kimberling, Jun 16 2018
STATUS
approved