This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A186927 Lesser of two consecutive 3-smooth numbers having no common divisors. 4
 1, 2, 3, 8, 27, 243, 2048, 524288, 129140163, 68630377364883, 36472996377170786403, 19342813113834066795298816, 706965049015104706497203195837614914543357369, 13703277223523221219433362313025801636536040755174924956117940937101787 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS a(n) = A003586(A186771(n)); A186928(n) = A003586(A186771(n) + 1). Subsequence of A006899: all terms are either powers of 2 or of 3. Najman improves an algorithm of Bauer & Bennett for computing the function that measures the minimal gap size f(k) in the sequence of integers at least one of whose prime factors exceeds k. This allows us to compute values of f(k) for larger k and obtain new values of f(k). - Jonathan Vos Post, Aug 18 2011 LINKS Charles R Greathouse IV, Table of n, a(n) for n = 1..21 M. Bauer and M. A. Bennett, Prime factors of consecutive integers, Mathematics of Computation 77 (2008), pp. 2455-2459. Charles R Greathouse IV, Illustration of n, a(n) for n = 1..33 Filip Najman, Large strings of consecutive smooth integers, Aug 18, 2011 MATHEMATICA smoothNumbers[p_, max_] := Module[{a, aa, k, pp, iter}, k = PrimePi[p]; aa = Array[a, k]; pp = Prime[Range[k]]; iter = Table[{a[j], 0, PowerExpand @ Log[pp[[j]], max/Times @@ (Take[pp, j - 1]^Take[aa, j - 1])]}, {j, 1, k}]; Table[Times @@ (pp^aa), Sequence @@ iter // Evaluate] // Flatten // Sort]; sn = smoothNumbers[3, 10^100]; Reap[For[i = 1, i <= Length[sn] - 1, i++, If[CoprimeQ[sn[[i]], sn[[i + 1]]], Sow[sn[[i]]]]]][[2, 1]] (* Jean-François Alcover, Nov 11 2016 *) CROSSREFS Cf. A186711. Sequence in context: A080568 A091339 A006277 * A177010 A300484 A004106 Adjacent sequences:  A186924 A186925 A186926 * A186928 A186929 A186930 KEYWORD nonn AUTHOR Charles R Greathouse IV and Reinhard Zumkeller, Mar 01 2011 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified August 25 15:34 EDT 2019. Contains 326324 sequences. (Running on oeis4.)