OFFSET
1,1
COMMENTS
Obviously all terms are composite, because for primes the difference is zero. - R. J. Mathar, Feb 01 2023
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
EXAMPLE
If n = 10 then the prime divisors are 2 and 5 and the difference between these two is 3 which is also a prime. So 10 is in the sequence.
If n = 70 then the prime divisors are 2, 5 and 7 and the difference between the largest and the smallest distinct prime divisors is 5 which is also a prime. So 70 is in the sequence.
MATHEMATICA
Select[Range[2, 300], Not[Length[FactorInteger[ # ]]==1]&&PrimeQ[FactorInteger[ # ][[ -1, 1]] -FactorInteger[ # ][[1, 1]]] &] (* Stefan Steinerberger, Jun 06 2006 *)
pQ[n_]:=Module[{fi=FactorInteger[n]}, Length[fi]>1&&PrimeQ[fi[[-1, 1]]-fi[[1, 1]]]]; Select[Range[250], pQ] (* Harvey P. Dale, Nov 19 2019 *)
CROSSREFS
KEYWORD
nonn,less
AUTHOR
Parthasarathy Nambi, Jun 05 2006
EXTENSIONS
Corrected and extended by Stefan Steinerberger, Jun 06 2006
STATUS
approved