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).

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

Links

Table of n, a(n) for n=1..90.

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

Adjacent sequences: A137476 A137477 A137478 * A137480 A137481 A137482

Keyword

nonn,easy

Author

Vladimir Joseph Stephan Orlovsky, Apr 22 2008

Extensions

More terms from R. J. Mathar, May 05 2008

Status

approved