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 A163990 Square array read by antidiagonals where the row n lists the numbers k such that their largest divisor <= sqrt(k) equals n. 6
 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 (list; table; graph; refs; listen; history; text; internal format)
 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 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: A289506 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

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Last modified September 28 09:16 EDT 2021. Contains 347714 sequences. (Running on oeis4.)