login
A377181
Rectangular array, by antidiagonals: (row 1) = r(1) = A002808 (composite numbers); (row n) = r(n) = A002808(r(n-1)) for n>=1.
1
4, 6, 9, 8, 12, 16, 9, 15, 21, 26, 10, 16, 25, 33, 39, 12, 18, 26, 38, 49, 56, 14, 21, 28, 39, 55, 69, 78, 15, 24, 33, 42, 56, 77, 94, 106, 16, 25, 36, 49, 60, 78, 105, 125, 141, 18, 26, 38, 52, 69, 84, 106, 140, 164, 184, 20, 28, 39, 55, 74, 94, 115, 141, 183, 212, 236
OFFSET
1,1
FORMULA
A059981(n) = number of appearances of A002808(n).
EXAMPLE
corner:
4 6 8 9 10 12 14 15 16 18
9 12 15 16 18 21 24 25 26 28
16 21 25 26 28 33 36 38 39 42
26 33 38 39 42 49 52 55 56 60
39 49 55 56 60 69 74 77 78 84
56 69 77 78 84 94 100 105 106 115
78 94 105 106 115 125 133 140 141 152
MATHEMATICA
c[n_] := c[n] = Select[Range[500], CompositeQ][[n]]
r[0] = Table[c[n], {n, 1, 10}]
r[n_] := r[n] = c[r[n - 1]]
Grid[Table[r[n], {n, 0, 6}]] (* array *)
p[n_, k_] := r[n][[k]];
Table[p[n - k + 1, k], {n, 0, 9}, {k, n + 1, 1, -1}] // Flatten (* sequence *)
CROSSREFS
Cf. A002808 (row 1), A050545 (row 2), A280327 (row 3), A006508 (column 1), A022450 (column 2), A023451 (column 3), A059981, A236356, A280327 (principal diagonal), A377173, A114577 (dispersion of the composite numbers).
Sequence in context: A085088 A073870 A236025 * A218036 A236536 A084335
KEYWORD
nonn,tabl
AUTHOR
Clark Kimberling, Oct 19 2024
STATUS
approved