A186711 Greatest common divisor of the n-th and (n+1)st 3-smooth numbers.

1, 1, 1, 2, 2, 1, 3, 4, 2, 6, 3, 1, 4, 12, 6, 2, 8, 9, 3, 12, 4, 16, 18, 6, 24, 27, 1, 32, 36, 12, 48, 54, 2, 64, 72, 81, 3, 96, 108, 4, 128, 144, 162, 6, 192, 216, 8, 1, 9, 288, 324, 12, 384, 432, 16, 2, 18, 576, 648, 24, 3, 27, 864, 32, 4, 36, 1152, 1296, 48, 6, 54, 1728, 64, 8, 72, 9, 81, 2592, 96, 12

Offset

1,4

Comments

A186712 shows where this function and the 3-smooth numbers A003586 are in the same range: a(A186712(n)) = A003586(n) and a(m) != A003586(n) for m < A186712(n).

Links

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

Formula

a(n) = A050873(A003586(n+1), A003586(n)).

a(A186771(n)) = 1.

Maple

A186711 := proc(n) igcd(A003586(n), A003586(n+1)) ; end proc: # R. J. Mathar, Feb 28 2011

Mathematica

S3 = Select[Range[3*10^4], FactorInteger[#][[-1, 1]] <= 3&]; Table[GCD[ S3[[n]], S3[[n+1]] ], {n, 1, Length[S3]-1}] (* Jean-François Alcover, Feb 02 2018 *)

Prog

(Haskell)
a186711 n = a186711_list !! (n-1)
a186711_list = zipWith gcd a003586_list $ tail a003586_list

Crossrefs

Cf. A003586, A050873, A061987, A186771.

Sequence in context: A368296 A103923 A349432 * A061987 A323899 A182630

Adjacent sequences: A186708 A186709 A186710 * A186712 A186713 A186714

Keyword

nonn

Author

Reinhard Zumkeller, Feb 26 2011

Status

approved