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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
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.
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
KEYWORD
nonn,look
AUTHOR
Rémy Sigrist, Mar 14 2019
STATUS
approved