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

1,2

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).

Links

Table of n, a(n) for n=1..70.

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]

Formula

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

Example

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.

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.

Sequence in context: A363268 A213778 A095833 * A082156 A283941 A285090

Adjacent sequences: A163987 A163988 A163989 * A163991 A163992 A163993

Keyword

nonn,tabl

Author

Omar E. Pol, Aug 11 2009

Status

approved