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A186711 Greatest common divisor of the n-th and (n+1)st 3-smooth numbers. 6
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 (list; graph; refs; listen; history; text; internal format)
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: A035317 A103923 A349432 * A061987 A323899 A182630

Adjacent sequences: A186708 A186709 A186710 * A186712 A186713 A186714

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Feb 26 2011

STATUS

approved

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Last modified December 5 02:30 EST 2022. Contains 358572 sequences. (Running on oeis4.)