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A321494 Numbers k such that k and k+1 have at least 4 but not both exactly 4 distinct prime factors. 7
38570, 40754, 51414, 51765, 58695, 60605, 62985, 66044, 68585, 70889, 71070, 73185, 73814, 74865, 77349, 82004, 83265, 83720, 83979, 85085, 87009, 90804, 90915, 91805, 91884, 92378, 94094, 94829, 96459, 97565, 98769, 98889, 100814, 101269, 101660, 104005, 104754, 105468, 107184, 108030, 108185, 108965 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
A321504 lists numbers n such that k and k+1 both have at least 4 distinct prime factors, while A140078 lists numbers such that k and k+1 have exactly 4 distinct prime factors. This sequence is the complement of the latter in the former, it consists of terms with indices (124, 214, 219, 276, 321, 415, ...) of the former.
LINKS
FORMULA
MATHEMATICA
aQ[n_]:=Module[{v={PrimeNu[n], PrimeNu[n+1]}}, Min[v]>3 && v!={4, 4}]; Select[Range[120000], aQ] (* Amiram Eldar, Nov 12 2018 *)
PROG
(PARI) is(n)=vecmin(n=[omega(n), omega(n+1)])>=4&&n!=[4, 4]
CROSSREFS
Cf. A140078, A321504; A321493, A321496 (analog for 3 & 5 factors).
Sequence in context: A362217 A330427 A289824 * A252103 A074484 A186583
KEYWORD
nonn
AUTHOR
M. F. Hasler, Nov 12 2018
STATUS
approved

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Last modified July 19 16:24 EDT 2024. Contains 374410 sequences. (Running on oeis4.)