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A137479
Greatest common divisor of (the average of the n-th twin prime pair) and (the average of the (n+1)st twin prime pair).
1
2, 6, 6, 6, 6, 6, 12, 6, 6, 6, 6, 30, 12, 6, 6, 12, 30, 6, 6, 12, 12, 12, 6, 6, 6, 30, 6, 6, 6, 30, 6, 6, 6, 6, 6, 12, 6, 6, 6, 12, 6, 6, 6, 6, 6, 12, 12, 6, 6, 24, 12, 12, 6, 6, 6, 12, 6, 6, 6, 6, 6, 6, 6, 24, 6, 6, 6, 6, 42, 30, 6, 6, 6, 6, 6, 24, 6, 30, 6, 6, 30, 120, 48, 12, 6, 6, 30, 30, 12, 6
OFFSET
1,1
FORMULA
a(n) = gcd(A014574(n), A014574(n+1)). - R. J. Mathar, May 05 2008
EXAMPLE
The averages of twin prime pairs in A014574 are 4, 6, 12, 18, 30, 42, ...
The sequence contains gcd(4, 6) = 2, gcd(6, 12) = 6, gcd(12,18) = 6, gcd(18,30) = 6, etc.
MAPLE
A137479 := proc(n) igcd( A014574(n), A014574(n+1)) ; end: # R. J. Mathar, May 05 2008
MATHEMATICA
GCD[a = Select[Range[5, 998], PrimeQ[ # - 1] && PrimeQ[ # + 1] &], b = Select[Range[4, 881], PrimeQ[ # - 1] && PrimeQ[ # + 1] &]]
CROSSREFS
Sequence in context: A134201 A184408 A184409 * A304363 A247097 A258576
KEYWORD
nonn,easy
AUTHOR
EXTENSIONS
More terms from R. J. Mathar, May 05 2008
STATUS
approved