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A318896
Numbers k such that k and k+1 are the product of exactly four distinct primes.
6
7314, 8294, 8645, 11570, 13629, 13845, 15105, 15554, 16554, 17390, 17654, 18290, 19005, 20405, 20769, 21489, 22010, 22154, 23001, 23114, 23529, 24530, 24765, 24870, 24969, 25346, 26690, 26894, 26961, 27434, 27965, 28105, 29145, 29210, 29414, 29469, 29666, 30414
OFFSET
1,1
COMMENTS
This sequence is different from A140078. For example, A140078(4) = 9009 = 3^2 * 7 * 11 * 13 is not a term.
LINKS
EXAMPLE
n | a(n) | a(n)+1
--+-------------------------+-------------------------
1 | 7314 = 2 * 3 * 23 * 53 | 7315 = 5 * 7 * 11 * 19
2 | 8294 = 2 * 11 * 13 * 29 | 8295 = 3 * 5 * 7 * 79
3 | 8645 = 5 * 7 * 13 * 19 | 8646 = 2 * 3 * 11 * 131
PROG
(PARI) is(n) = omega(n)==4 && omega(n+1)==4 && bigomega(n)==4 && bigomega(n+1)==4 \\ Felix Fröhlich, Sep 05 2018
(PARI) is(n) = factor(n)[, 2]~ == [1, 1, 1, 1] && factor(n+1)[, 2]~ == [1, 1, 1, 1] \\ David A. Corneth, Sep 06 2018
CROSSREFS
Subsequence of A140078.
Sequence in context: A116248 A140078 A321504 * A328786 A295004 A202167
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Sep 05 2018
STATUS
approved