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A321487 Numbers in A121707 (n^3 > 1 divides Sum_{k=1..n-1} k^n) which are not semiprimes. 3
275, 455, 475, 539, 575, 715, 775, 875, 935, 1075, 1127, 1175, 1235, 1295, 1375, 1421, 1463, 1475, 1495, 1547, 1595, 1615, 1675, 1715, 1775, 1859, 1955, 1975, 2009, 2015, 2035, 2057, 2075, 2093, 2135, 2255, 2261, 2299, 2303, 2375, 2387, 2555, 2575, 2597, 2635, 2639, 2675, 2717, 2783 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Most terms of A121707 and its (conjectured) subsequence A267999 are semiprimes. This sequence lists the exceptions.
At first, it looked as if most terms were multiples of 5. The first exceptions are a({4, 11, 16}) = {539, 1127, 1421}. However, after the first 30 terms, almost every other term is not divisible by 5.
The first terms not in A267999 are {2057, 2873, 3689, 4015, 4991, 6137, ...}, cf. A321488.
LINKS
CROSSREFS
Sequence in context: A062377 A157489 A144715 * A250736 A063368 A028531
KEYWORD
nonn
AUTHOR
M. F. Hasler, Nov 11 2018
STATUS
approved

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Last modified April 18 08:27 EDT 2024. Contains 371769 sequences. (Running on oeis4.)