A249327 - OEIS

A249327

Rectangular array T(n,k) = f(n)*k^2, where f = A005117 (squarefree numbers); n, k >= 1; read by antidiagonals.

1, 4, 2, 9, 8, 3, 16, 18, 12, 5, 25, 32, 27, 20, 6, 36, 50, 48, 45, 24, 7, 49, 72, 75, 80, 54, 28, 10, 64, 98, 108, 125, 96, 63, 40, 11, 81, 128, 147, 180, 150, 112, 90, 44, 13, 100, 162, 192, 245, 216, 175, 160, 99, 52, 14, 121, 200, 243, 320, 294, 252, 250

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OFFSET

1,2

COMMENTS

Every positive integer occurs exactly once.

LINKS

Table of n, a(n) for n=1..62.

FORMULA

T(1,k) = A000290(k), T(2,k) = A001105(k), T(3,k) = A033428(k), T(4,k) = A033429(k), T(5,.) through T(10,.) are A033581, A033582, A033583, A033584, A152742 and A144555 without initial 0. - M. F. Hasler, Oct 31 2014

EXAMPLE

Northwest corner:

1 4 9 16 25 36 49

2 8 18 32 50 72 98

3 12 27 48 75 108 147

5 20 45 80 125 180 245

6 24 54 96 150 216 294

MATHEMATICA

z = 20; f = Select[Range[10000], SquareFreeQ[#] &];

u[n_, k_] := f[[n]]*k^2; t = Table[u[n, k], {n, 1, 20}, {k, 1, 20}];

TableForm[t] (* A249327 array *)

Table[u[k, n - k + 1], {n, 1, 15}, {k, 1, n}] // Flatten (* A249327 sequence *)

CROSSREFS

Cf. A005117, A000037 (is partitioned by the rows of A249327, excluding the first).

Sequence in context: A243968 A104583 A278103 * A182728 A290538 A097664

Adjacent sequences: A249324 A249325 A249326 * A249328 A249329 A249330

KEYWORD

nonn,tabl,easy

AUTHOR

Clark Kimberling, Oct 26 2014

STATUS

approved