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A108128
Number of distinct prime factors of concatenated twin primes.
0
2, 2, 2, 2, 2, 2, 3, 2, 3, 2, 2, 2, 2, 2, 2, 3, 2, 3, 2, 3, 3, 3, 3, 3, 3, 2, 2, 3, 2, 2, 3, 2, 2, 3, 2, 3, 3, 2, 2, 2, 3, 2, 3, 3, 3, 3, 2, 3, 2, 4, 3, 2, 2, 3, 2, 2, 2, 2, 3, 3, 2, 2, 3, 2, 2, 3, 2, 3, 3, 2, 2, 2, 3, 2, 2, 3, 2, 2, 3, 2, 3, 3, 2, 3, 4, 2, 2, 3, 3, 3, 3, 3, 2, 2, 3, 2, 2, 3, 3, 2, 2, 3, 2, 3, 2
OFFSET
1,1
EXAMPLE
The number of distinct prime factors of 35 (which is obtained from concatenating the twin primes 3 and 5) is 2, which is the first term of the sequence.
MATHEMATICA
Length[ FactorInteger[ # ]] & /@ FromDigits /@ Transpose[{Select[ Prime[ Range[550]], PrimeQ[ # + 2] &], Select[ Prime[ Range[550]], PrimeQ[ # - 2] &]}] (* Robert G. Wilson v, Jun 09 2005 *)
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Parthasarathy Nambi, Jun 04 2005
EXTENSIONS
Edited, corrected and extended by Robert G. Wilson v, Jun 09 2005
STATUS
approved