The OEIS mourns the passing of Jim Simons and is grateful to the Simons Foundation for its support of research in many branches of science, including the OEIS.
The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A216664 Odd numbers n such that the decimal expansion of 1/n contains the digit "9" at position (n + 1)/2. 2
 11, 17, 19, 23, 29, 47, 59, 61, 73, 91, 95, 97, 101, 103, 109, 113, 127, 131, 137, 139, 149, 167, 179, 181, 189, 193, 211, 223, 229, 233, 251, 255, 257, 263, 269, 313, 325, 331, 337, 349, 353, 367, 379, 383, 389, 419, 421, 433, 441, 457, 461, 463, 477, 487, 491 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS First nine terms are primes. This is not a subsequence of A187040: 189 belongs to this sequence but not to A187040. LINKS Arkadiusz Wesolowski, Table of n, a(n) for n = 1..1000 Wikipedia, Midy's theorem Index entries for sequences related to decimal expansion of 1/n EXAMPLE 1/17 = .058823529..., therefore 17 is a term. 1/21 = .04761904761..., therefore 21 is not a term. MATHEMATICA lst = {}; Do[l = (n + 1)/2; d = Flatten@RealDigits[1/n, 10, l]; If[Join[Table[0, {-1*Last@d}], Most@d][[l]] == 9, AppendTo[lst, n]], {n, 1, 491, 2}]; lst PROG (PARI) forstep(n=1, 491, 2, s=(n+1)/2; "\p s"; if(Mod(floor(10^s/n), 10)==9, print1(n, ", "))); \\ Arkadiusz Wesolowski, Aug 23 2013 (Python) from itertools import count, islice def A216664_gen(startvalue=1): # generator of terms >= startvalue for n in count(max(startvalue+1-startvalue%2, 1), 2): if 10**((n+1)//2)//n % 10 == 9: yield n A216664_list = list(islice(A216664_gen(), 20)) # Chai Wah Wu, Mar 04 2022 CROSSREFS Cf. A187040. Sequence in context: A050778 A316100 A049593 * A019412 A178641 A226682 Adjacent sequences: A216661 A216662 A216663 * A216665 A216666 A216667 KEYWORD base,nonn AUTHOR Arkadiusz Wesolowski, Sep 14 2012 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified June 15 11:51 EDT 2024. Contains 373407 sequences. (Running on oeis4.)