A112757 Greatest common divisors of consecutive 5-smooth numbers.

1, 1, 1, 1, 1, 2, 1, 1, 2, 3, 1, 2, 2, 4, 1, 1, 3, 2, 4, 4, 5, 3, 2, 2, 6, 4, 8, 3, 5, 1, 9, 6, 4, 4, 12, 5, 1, 1, 9, 6, 10, 2, 18, 12, 8, 8, 9, 15, 3, 1, 2, 2, 18, 12, 20, 4, 36, 15, 3, 16, 5, 27, 18, 30, 6, 2, 4, 4, 36, 24, 25, 5, 8, 27, 45, 9, 3, 6, 32, 10, 54, 36, 60, 12, 4, 8, 8, 45, 9, 48, 15, 5

Offset: 1

Author

Reinhard Zumkeller, Sep 18 2005

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..750 from Harvey P. Dale)

Crossrefs

Cf. A051037, A112752.

Programs

Mathematica

GCD@@#&/@(Partition[Select[Range[2000],Max[Transpose[ FactorInteger[ #]] [[1]]]<6&],2,1]) (* Harvey P. Dale, Dec 24 2015 *)

Formula

a(n) = gcd(A051037(n), A051037(n+1)).