A163990 Square array read by antidiagonals where the row n lists the numbers k such that their largest divisor <= sqrt(k) equals n.

1, 4, 2, 9, 6, 3, 16, 12, 8, 5, 25, 20, 15, 10, 7, 36, 30, 24, 18, 14, 11, 49, 42, 35, 28, 21, 22, 13, 64, 56, 48, 40, 32, 27, 26, 17, 81, 72, 63, 54, 45, 44, 33, 34, 19, 100, 90, 80, 70, 60, 50, 52, 39, 38, 23, 121, 110, 99, 88, 77, 66, 55, 68, 51, 46, 29, 144, 132, 120, 108

Offset: 1

Author

Omar E. Pol, Aug 11 2009

Keywords

• nonn
• tabl

Comments

This sequence is a permutation of the natural numbers.

Note that the first row is formed by 1 together the prime numbers and the first column are the squares of the natural numbers.

For more information see A163280, the main entry for this sequence. (See also A161344).

Examples

			Array begins:
1, 2, 3, 5, 7, 11,
4, 6, 8, 10, 14,
9, 12, 15, 18,
16, 20, 24,
25, 30,
36,
See also the array in A163280.
		

Links

• Index entries for sequences that are permutations of the natural numbers
• Omar E. Pol, Illustration for A008578, the first row of the array [From _Omar E. Pol_, Oct 24 2009]
• Omar E. Pol, Illustration for A161344, the second row of the array [From _Omar E. Pol_, Oct 24 2009]
• Omar E. Pol, Illustration for A008578, A161344, A161345 and A161424 [From _Omar E. Pol_, Oct 24 2009]

Crossrefs

Cf. A000027, A000040, A033676, A147861, A163100, A163280, A163281, A163991, A164000.

Cf. Rows: 1=A008578, 2=A161344, 3=A161345, 4=A161424, 5=A161835, 6=A162526, 7=A162527, 8=A162528, 9=A162529, 10=A162530, 11=A162531, 12=A162532.

Cf. Columns: 1=A000290, 2=A002378, 4=A164004, 6=A164006, 7=A164007, 8=A164008, 9=A164009, 10=A164010, 11=A164011, 12=A164012.

Formula

Row n lists the numbers k such that A033676(k)=n.