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!)
 A156589 a(n) = 4^n - 2^n - 1. 2
 -1, 1, 11, 55, 239, 991, 4031, 16255, 65279, 261631, 1047551, 4192255, 16773119, 67100671, 268419071, 1073709055, 4294901759, 17179738111, 68719214591, 274877382655, 1099510579199, 4398044413951, 17592181850111, 70368735789055 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS Sequence A098845 lists indices of primes, i.e., a(n) prime <=> n=A098845(k) for some k. Starting with n=2, binary numbers of the form (n-1)0(n) where n is the index and the number of 1's. It can also be formed by appending a 1 to the right of each term of A129868. 1/a(n) = Sum_{m>0} A000045(m)*2^(-n(m+1)) for n > 0. E.g., 1/a(4) = 0.0000 0001 0001 0010 0011 0101 1000 ... in binary. - Lee A. Newberg, Apr 12 2018 LINKS Vincenzo Librandi, Table of n, a(n) for n = 0..500 Index entries for linear recurrences with constant coefficients, signature (7,-14,8). FORMULA G.f.: ( 1-8*x+10*x^2 ) / ( (-1+x)*(2*x-1)*(4*x-1) ). - R. J. Mathar, Oct 21 2014 MATHEMATICA Table[4^n - 2^n - 1, {n, 0, 25}] (* Vincenzo Librandi, Apr 13 2018 *) PROG (PARI) vector(99, n, 4^n-2^n-1) (MAGMA) [4^n-2^n-1: n in [0..30]]; // Vincenzo Librandi, Apr 13 2018 CROSSREFS Cf. A000045, A098845, A129868. Sequence in context: A072025 A098992 A246990 * A165791 A032166 A218000 Adjacent sequences:  A156586 A156587 A156588 * A156590 A156591 A156592 KEYWORD sign,easy AUTHOR M. F. Hasler, Feb 10 2009 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 May 7 10:18 EDT 2021. Contains 343650 sequences. (Running on oeis4.)