The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A036490 Numbers whose prime factors are in {5, 7, 11}. 3
 5, 7, 11, 25, 35, 49, 55, 77, 121, 125, 175, 245, 275, 343, 385, 539, 605, 625, 847, 875, 1225, 1331, 1375, 1715, 1925, 2401, 2695, 3025, 3125, 3773, 4235, 4375, 5929, 6125, 6655, 6875, 8575, 9317, 9625, 12005, 13475, 14641, 15125, 15625, 16807 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 REFERENCES G. E. Andrews, The Theory of Partitions, Addison-Wesley, 1976, p. 160. LINKS Reinhard Zumkeller, Table of n, a(n) for n = 1..1000 FORMULA Sum_{n>=1} 1/a(n) = (5*7*11)/((5-1)*(7-1)*(11-1)) - 1 = 29/48. - Amiram Eldar, Sep 24 2020 a(n) ~ exp((6*log(5)*log(7)*log(11)*n)^(1/3)) / sqrt(385). - Vaclav Kotesovec, Sep 24 2020 MATHEMATICA Select[Range[20000], (fi = FactorInteger[#][[All, 1]]; Intersection[fi, {5, 7, 11}] == fi)&] (* or, for a large number of terms: *) f[pp_(* primes *), max_(* maximum term *)] := Module[{a, aa, k, iter}, k = Length[pp]; aa = Array[a, 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]; A036490 = f[{5, 7, 11}, 2*10^14] // Rest (* Jean-François Alcover, Sep 19 2012, updated Nov 12 2016 *) PROG (Haskell) import Data.Set (Set, fromList, insert, deleteFindMin) a036490 n = a036490_list !! (n-1) a036490_list = f \$ fromList [5, 7, 11] where    f s = m : (f \$ insert (5 * m) \$ insert (7 * m) \$ insert (11 * m) s')          where (m, s') = deleteFindMin s -- Reinhard Zumkeller, Feb 19 2013 CROSSREFS Cf. A036491, A036492. Sequence in context: A218394 A067289 A036491 * A106330 A057247 A157437 Adjacent sequences:  A036487 A036488 A036489 * A036491 A036492 A036493 KEYWORD nonn,easy AUTHOR EXTENSIONS Offset corrected by Reinhard Zumkeller, Feb 19 2013 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 October 24 07:04 EDT 2020. Contains 337975 sequences. (Running on oeis4.)