This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A232769 Numbers n not divisible by 9 such that n divides 10^n - 1 (A014950). 2
 1, 3, 111, 4107, 151959, 5622483, 22494039, 208031871, 225121209, 832279443, 7697179227, 8329484733, 27486820443, 30794339391, 92366302683, 123199851603, 230915528769, 284795631399, 308190935121, 1017012356391 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS The above terms reduced modulo 9 yield: 1, 3, 3, 3, 3, 3, 6, 3, 6, 6, 3, 6, 3, 6, 3, 3, 3, 3, 6, 3, 6, …, . The only primes less than a billion which can divide members of this sequence are 3, 37, 5477, 607837, 1519591, 2028119, 15195911, 18235093, 44988079, 74202397, 247629013, 337349203, 395397319, 462411133, and 674699071. - Charles R Greathouse IV, Dec 03 2013 LINKS Ray Chandler, Table of n, a(n) for n = 1..55 MATHEMATICA k = 3; lst = {1}; While[k < 10^10 + 1, If[ PowerMod[10, k, k] == 1, AppendTo[ lst, k]; Print@ k]; k += 3; If[ PowerMod[ 10, k, k] == 1, AppendTo[ lst, k]; Print@ k]; k += 6]; lst PROG (PARI) is(n)=n%9 && Mod(10, n)^n==1 \\ Charles R Greathouse IV, Dec 03 2013 (PARI) forstep(n=1, 1e8, [2, 4, 4, 2, 4, 2, 2, 2, 6, 2, 2, 4, 2, 2, 2, 4, 2, 2, 2, 4, 2, 2, 6, 2, 2, 2, 4, 2, 4, 4, 2, 2], if(Mod(10, n)^n==1, print1(n", "))) \\ Charles R Greathouse IV, Dec 03 2013 CROSSREFS Cf. A014950. Sequence in context: A111091 A301612 A180765 * A066138 A114207 A128684 Adjacent sequences:  A232766 A232767 A232768 * A232770 A232771 A232772 KEYWORD nonn AUTHOR Hans Havermann and Robert G. Wilson v, Nov 29 2013 EXTENSIONS a(22)-a(26) from Ray Chandler, Dec 11 2013 B-file extended through a(55) by Ray Chandler, Dec 24 2013 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 October 18 13:31 EDT 2019. Contains 328161 sequences. (Running on oeis4.)