OFFSET
1,1
COMMENTS
Prime factors counted with multiplicity. - Harvey P. Dale, May 07 2023
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
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
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Apr 14 2005
STATUS
approved