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

 Please make a donation to keep the OEIS running. We are now in our 56th year. In the past year we added 10000 new sequences and reached almost 9000 citations (which often say "discovered thanks to the OEIS"). Other ways to donate

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A003596 Numbers of the form 2^i*11^j. 21
 1, 2, 4, 8, 11, 16, 22, 32, 44, 64, 88, 121, 128, 176, 242, 256, 352, 484, 512, 704, 968, 1024, 1331, 1408, 1936, 2048, 2662, 2816, 3872, 4096, 5324, 5632, 7744, 8192, 10648, 11264, 14641, 15488, 16384, 21296, 22528, 29282, 30976, 32768 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS A204455(11*a(n)) = 11, and only for these numbers. - Wolfdieter Lang, Feb 04 2012 LINKS Vincenzo Librandi and Charles R Greathouse IV, Table of n, a(n) for n = 1..10000 (first 100 terms from Librandi) FORMULA The characteristic function of this sequence is given by Sum_{n >= 1} x^a(n) = Sum_{n >= 1} mu(22*n)*x^n/(1 - x^n), where mu(n) is the Möbius function A008683. Cf. with the formula of Hanna in A051037. - Peter Bala, Mar 18 2019 Sum_{n>=1} 1/a(n) = (2*11)/((2-1)*(11-1)) = 11/5. - Amiram Eldar, Sep 23 2020 a(n) ~ exp(sqrt(2*log(2)*log(11)*n)) / sqrt(22). - Vaclav Kotesovec, Sep 23 2020 MATHEMATICA fQ[n_] := PowerMod[22, n, n]==0; Select[Range[40000], fQ] (* Vincenzo Librandi, Feb 04 2012 *) PROG (PARI) list(lim)=my(v=List(), N); for(n=0, log(lim)\log(11), N=11^n; while(N<=lim, listput(v, N); N<<=1)); vecsort(Vec(v)) \\ Charles R Greathouse IV, Jun 28 2011 (Haskell) import Data.Set (singleton, deleteFindMin, insert) a003596 n = a003596_list !! (n-1) a003596_list = f \$ singleton (1, 0, 0) where    f s = y : f (insert (2 * y, i + 1, j) \$ insert (11 * y, i, j + 1) s')          where ((y, i, j), s') = deleteFindMin s -- Reinhard Zumkeller, May 15 2015 (MAGMA) [n: n in [1..2*10^5] | PrimeDivisors(n) subset [2, 11]]; // Vincenzo Librandi, Jun 27 2016 (GAP) Filtered([1..33000], n->PowerMod(22, n, n)=0); # Muniru A Asiru, Mar 19 2019 CROSSREFS Cf. A025612, A025616, A025621, A025625, A025629, A025632, A025634, A025635, A108761, A003597, A107988, A003598, A108698, A003599, A107788, A108687, A108779, A108090. Sequence in context: A115797 A336627 A242313 * A018600 A018408 A018320 Adjacent sequences:  A003593 A003594 A003595 * A003597 A003598 A003599 KEYWORD nonn,easy AUTHOR 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 November 25 11:32 EST 2020. Contains 338623 sequences. (Running on oeis4.)