The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 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 A321504 \ A140078. 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: A250712 A330427 A289824 * A252103 A074484 A186583 Adjacent sequences:  A321491 A321492 A321493 * A321495 A321496 A321497 KEYWORD nonn AUTHOR M. F. Hasler, Nov 12 2018 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified May 27 21:52 EDT 2020. Contains 334671 sequences. (Running on oeis4.)