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

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 56th year, we are closing in on 350,000 sequences, and we’ve crossed 9,700 citations (which often say “discovered thanks to the OEIS”).

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A339345 Lexicographically earliest sequence of odd numbers such that the asymptotic density of the numbers which are coprime to all the terms of this sequence is 1/2. 2
 1, 3, 5, 9, 15, 17, 25, 27, 45, 51, 75, 81, 85, 125, 135, 153, 225, 243, 255, 257, 289, 375, 405, 425, 459, 625, 675, 729, 765, 771, 867, 1125, 1215, 1275, 1285, 1377, 1445, 1875, 2025, 2125, 2187, 2295, 2313, 2601, 3125, 3375, 3645, 3825, 3855, 4131, 4335, 4369 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Numbers whose prime divisors are all in A339344. Closed under multiplication. First differs from A143512 and A174688 at n = 970. LINKS Amiram Eldar, Table of n, a(n) for n = 1..10000 FORMULA Sum_{n>=1} 1/a(n) = 2. MATHEMATICA seq[m_] := Module[{v = {1}, r = 1, p = 3, k, n = m + 1, s = {1}, v1, s1, s2, rmax}, Do[AppendTo[v, p]; r *= 1 - 1/p; p = NextPrime[r/(r - 1/2)], {m}]; vmax = v[[-1]]; Do[v1 = v[[k]]; rmax = Floor[Log[vmax]/Log[v1]]; s1 = v1^Range[0, rmax]; s2 = Select[Union[Flatten[Outer[Times, s, s1]]], # <= vmax &]; s = Union[s, s2], {k, 2, n}]; s]; seq[5] CROSSREFS Cf. A143512, A174688, A339344. Sequence in context: A093688 A143512 A174688 * A111249 A190804 A100812 Adjacent sequences:  A339342 A339343 A339344 * A339346 A339347 A339348 KEYWORD nonn AUTHOR Amiram Eldar, Nov 30 2020 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 December 2 23:30 EST 2021. Contains 349445 sequences. (Running on oeis4.)