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 A306877 Lexicographically earliest sequence of distinct positive terms such that, for any n > 0, among the prime divisors of n * a(n) there are at least 4 runs of consecutive prime numbers. 1
 1870, 935, 1729, 1045, 374, 2093, 494, 1235, 2639, 187, 170, 2737, 190, 247, 4301, 1265, 110, 2821, 130, 209, 299, 85, 182, 3367, 418, 95, 3451, 377, 220, 5423, 230, 1495, 391, 55, 598, 3458, 238, 65, 133, 253, 260, 403, 266, 115, 5797, 91, 273, 3689, 741, 319 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS This sequence is a variant of A285744 and of A306864. This sequence is a self-inverse permutation of the natural numbers. LINKS Rémy Sigrist, Table of n, a(n) for n = 1..30000 Rémy Sigrist, PARI program for A306877 FORMULA A287170(n * a(n)) >= 4. EXAMPLE The first terms, alongside the corresponding runs, are:   n   a(n)  runs in n*a(n)   --  ----  --------------    1  1870  2, 5, 11, 17    2   935  2, 5, 11, 17    3  1729  3, 7, 13, 19    4  1045  2, 5, 11, 19    5   374  2, 5, 11, 17    6  2093  2-3, 7, 13, 23    7   494  2, 7, 13, 19    8  1235  2, 5, 13, 19    9  2639  3, 7, 13, 29   10   187  2, 5, 11, 17   11   170  2, 5, 11, 17   12  2737  2-3, 7, 17, 23   13   190  2, 5, 13, 19   14   247  2, 7, 13, 19   15  4301  3-5, 11, 17, 23   16  1265  2, 5, 11, 23 PROG (PARI) See Links section. CROSSREFS Cf. A285744, A287170, A306864. Sequence in context: A052168 A237152 A306864 * A073495 A073489 A232040 Adjacent sequences:  A306874 A306875 A306876 * A306878 A306879 A306880 KEYWORD nonn,look AUTHOR Rémy Sigrist, Mar 14 2019 STATUS approved

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Last modified January 19 20:41 EST 2020. Contains 331066 sequences. (Running on oeis4.)