The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A321970 Numbers k such that 7^k ends with k. 3
 3, 43, 343, 2343, 72343, 172343, 5172343, 65172343, 565172343, 1565172343, 11565172343, 511565172343, 5511565172343, 65511565172343, 265511565172343, 1265511565172343, 31265511565172343, 331265511565172343, 3331265511565172343, 43331265511565172343 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Leftmost digit of a(n) is A133617(n-1) for n <= 30. - Alois P. Heinz, Nov 26 2018 LINKS J. Jimenez Urroz and J. Luis A. Yebra, On the equation a^x == x (mod b^n), J. Int. Seq. 12 (2009) #09.8.8. EXAMPLE 7^3 = 343, and it ends with 3, so 3 is a term. MATHEMATICA a[1] = 3; a[n_] := a[n] = For[ida = IntegerDigits[a[n-1]]; k = 1, True, k++, idk = IntegerDigits[k]; pm = PowerMod[7, an = FromDigits[Join[idk, ida]], 10^IntegerLength[an]]; If[pm == an, Return[an]]]; Array[a, 20] (* after Jean-François Alcover in A064541 *) CROSSREFS Cf. A133617. Sequence A064541 is similar, but uses the smallest single-digit prime as a base, unlike this one, which uses the largest single-digit prime as a base. Sequence in context: A229695 A060559 A197778 * A199349 A197609 A199346 Adjacent sequences:  A321967 A321968 A321969 * A321971 A321972 A321973 KEYWORD nonn,base AUTHOR Ivan Stoykov, Nov 26 2018 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 May 25 16:32 EDT 2022. Contains 354071 sequences. (Running on oeis4.)