This site is supported by donations to The OEIS Foundation.

 Annual Appeal: Please make a donation to keep the OEIS running. In 2018 we replaced the server with a faster one, added 20000 new sequences, and reached 7000 citations (often saying "discovered thanks to the OEIS"). Other ways to donate

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A068425 a(n) = floor(2^n*Pi). 9
 1, 3, 6, 12, 25, 50, 100, 201, 402, 804, 1608, 3216, 6433, 12867, 25735, 51471, 102943, 205887, 411774, 823549, 1647099, 3294198, 6588397, 13176794, 26353589, 52707178, 105414357, 210828714, 421657428, 843314856, 1686629713 (list; graph; refs; listen; history; text; internal format)
 OFFSET -1,2 COMMENTS In other words, take the binary expansion of Pi, drop the decimal point and interpret the first n+2 bits as an integer. Dubickas proves that infinitely many terms of this sequence are divisible by 2 or 3 (and hence infinitely many composites). - Charles R Greathouse IV, Feb 04 2016 LINKS G. C. Greubel, Table of n, a(n) for n = -1..3300 ArtÅ«ras Dubickas, Prime and composite integers close to powers of a number, Monatsh. Math. 158:3 (2009), pp. 271-284. EXAMPLE The binary expansion of Pi (A004601) begins 1, 1. 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 0, 1, 1, 0, ... so we get 1, 3, 6, 12, 25, 50, ... MATHEMATICA Table[Floor[2^n*Pi], {n, -1, 100}] (* G. C. Greubel, Mar 23 2018 *) PROG (PARI) a(n)=floor(Pi<

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 18 23:46 EST 2018. Contains 318245 sequences. (Running on oeis4.)