The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

Thanks to everyone who made a donation during our annual appeal!
To see the list of donors, or make a donation, see the OEIS Foundation home page.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A288171 Lexicographically earliest sequence of distinct positive terms such that, for any n > 0, a(n)*a(n+3) has at least 5 distinct prime factors. 3
 1, 2, 3, 2310, 1155, 770, 4, 6, 9, 1365, 385, 910, 8, 12, 11, 1785, 455, 210, 10, 18, 13, 231, 595, 330, 20, 22, 7, 273, 105, 390, 30, 26, 14, 77, 165, 195, 60, 28, 34, 91, 255, 285, 66, 38, 42, 35, 315, 55, 78, 44, 84, 70, 345, 65, 33, 52, 102, 130, 357, 95 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS This sequence is a permutation of the natural numbers, with inverse A288800. See also A288164 for similar sequences. Conjecturally, a(n) ~ n. LINKS Rémy Sigrist, Table of n, a(n) for n = 1..25000 Rémy Sigrist, C++ program for A288171 EXAMPLE The first terms, alongside the primes p dividing a(n)*a(n+3), are: n       a(n)    p --      ----    -------------- 1       1       2, 3, 5, 7, 11 2       2       2, 3, 5, 7, 11 3       3       2, 3, 5, 7, 11 4       2310    2, 3, 5, 7, 11 5       1155    2, 3, 5, 7, 11 6       770     2, 3, 5, 7, 11 7       4       2, 3, 5, 7,     13 8       6       2, 3, 5, 7, 11 9       9       2, 3, 5, 7,     13 10      1365    2, 3, 5, 7,     13 11      385     2, 3, 5, 7, 11 12      910     2,    5, 7, 11, 13 13      8       2, 3, 5, 7,         17 14      12      2, 3, 5, 7,     13 15      11      2, 3, 5, 7, 11 16      1785    2, 3, 5, 7,         17 17      455     2, 3, 5, 7,     13 18      210     2, 3, 5, 7,     13 19      10      2, 3, 5, 7, 11 20      18      2, 3, 5, 7,         17 CROSSREFS Cf. A288164, A288800 (inverse). Sequence in context: A323518 A004909 A266585 * A137321 A066848 A324310 Adjacent sequences:  A288168 A288169 A288170 * A288172 A288173 A288174 KEYWORD nonn,look AUTHOR Rémy Sigrist, Jun 16 2017 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified January 18 19:59 EST 2021. Contains 340262 sequences. (Running on oeis4.)