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A105572 Numbers m such that m-3 and m+3 have 3 prime factors. 3
15, 47, 73, 95, 102, 113, 127, 150, 151, 167, 168, 185, 233, 239, 241, 258, 276, 282, 287, 289, 313, 319, 335, 360, 366, 407, 409, 415, 426, 431, 432, 433, 439, 480, 521, 527, 552, 558, 593, 599, 601, 606, 607, 612, 642, 648, 649, 654, 655, 660, 708, 713 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
A001222(a(n)-3) = A001222(a(n)+3) = 3.
Prime factors counted with multiplicity. - Harvey P. Dale, May 07 2023
LINKS
EXAMPLE
From Jon E. Schoenfield, Jan 19 2015: (Start)
73 - 3 = 70 = 2 * 5 * 7 and 73 + 3 = 76 = 2 * 2 * 19 so 73 is in the sequence.
81 - 3 = 78 = 2 * 3 * 13 but 81 + 3 = 84 = 2 * 2 * 3 * 7 so 81 is not in the sequence. (End)
MATHEMATICA
q=3; lst={}; Do[If[Plus@@Last/@FactorInteger[n-q]==q&&Plus@@Last/@FactorInteger[n+q]==q, AppendTo[lst, n]], {n, 7!}]; lst (* Vladimir Joseph Stephan Orlovsky, Feb 01 2009 *)
Flatten[Position[Partition[PrimeOmega[Range[800]], 7, 1], _?(#[[1]]==#[[7]]==3&), 1, Heads-> False]]+3 (* Harvey P. Dale, May 07 2023 *)
CROSSREFS
Sequence in context: A041438 A045111 A031451 * A143031 A214675 A166118
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Apr 14 2005
STATUS
approved

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Last modified May 26 05:37 EDT 2024. Contains 372807 sequences. (Running on oeis4.)