OFFSET
1,2
COMMENTS
The Sophie Germain prime numbers (A005384) are part of this sequence because when adding to one of them its only prime factor (itself) + 1 = 2*A005384 + 1 the result is another prime number (A005385)
Prime factors taken with multiplicity. - Harvey P. Dale, Sep 04 2024
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
FORMULA
a(n)+ prime factors of a(n) + 1 = p ; p is a prime number, member of A131102.
EXAMPLE
MATHEMATICA
Select[Range[400], PrimeQ[Total[Times@@@FactorInteger[#]]+#+1]&] (* Harvey P. Dale, Sep 04 2024 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Tomas Xordan, Jun 14 2007
STATUS
approved