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!)
 A227070 Powers n such that the set s(n) = {k > 0 such that k^n ends with k} does not occur for smaller n. 1
 1, 2, 3, 5, 6, 9, 11, 17, 21, 26, 33, 41, 51, 65, 81, 101, 126, 129, 161, 201, 251, 257, 321, 401, 501, 513, 626, 641, 801, 1001, 1025, 1251, 1281, 1601, 2001, 2049, 2501, 2561, 3126, 3201, 4001, 4097, 5001, 5121, 6251, 6401, 8001, 8193, 10001 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS These numbers might be called automorphic powers because the sets s(n) are called automorphic numbers. It appears that all numbers of the form 1 + 5^i are here. In fact, these appear to produce the only even numbers here. The set s(4) equals s(2). The set s(7) equals s(3). The set s(9) does not differ from s(5) until k = 10443. The set s(17) does not differ from s(9) until k = 108307. The sequence also has 126, 201, 251, 501, and 626, but there may be missing numbers. Entries a(17)-a(49) have been tentatively obtained by comparing the terms < 10^30 in the sets s(n), for 2 <= n <= 10001. - Giovanni Resta, Jul 30 2013 LINKS FORMULA Conjecture: a(n+1) = A003592(n) + 1. - Eric M. Schmidt, Jul 30 2013 MATHEMATICA ts = {}; t = {}; Do[s = Select[Range, PowerMod[#, n, 10^IntegerLength[#]] == # &]; If[! MemberQ[ts, s], Print[n]; AppendTo[ts, s]; AppendTo[t, n]], {n, 2, 101}]; t = Join[{1}, t] CROSSREFS Cf. A003226 (n=2), A033819 (n=3), A068407 (n=5), A068408 (n=6). Cf. A072496 (n=11), A072495 (n=21), A076650 (n=26). Cf. A227071. Sequence in context: A131995 A060714 A241819 * A032718 A086191 A074658 Adjacent sequences:  A227067 A227068 A227069 * A227071 A227072 A227073 KEYWORD nonn,hard,more,base AUTHOR T. D. Noe, Jul 29 2013 EXTENSIONS a(17)-a(49) from Giovanni Resta, Jul 30 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 April 9 06:54 EDT 2020. Contains 333344 sequences. (Running on oeis4.)