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!)
 A076947 Smallest k > 0 such that nk+1 is a cube. 4
 7, 13, 21, 31, 43, 57, 1, 91, 7, 133, 157, 183, 2, 52, 273, 307, 343, 19, 18, 463, 3, 553, 601, 651, 703, 1, 37, 26, 931, 993, 4, 1123, 1191, 1261, 38, 61, 27, 9, 105, 1723, 1807, 372, 5, 2071, 91, 2257, 2353, 2451, 119, 2653, 2757, 14, 2971, 127, 3193, 13, 6, 3541 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 REFERENCES Dorin Andrica, Vlad Crişan, The smallest nontrivial solution to x^k == 1 (mod n) ..., Amer. Math. Monthly 126 (2019), 173-178. LINKS Robert G. Wilson v, Table of n, a(n) for n = 1..1000 MATHEMATICA Do[k = 1; While[ !IntegerQ[(n*k + 1)^(1/3)], k++ ]; Print[k], {n, 1, 58}] f[n_] := Block[{x = 2}, While[ Mod[x^3 - 1, n] != 0, x++]; (x^3 - 1)/n]; Array[f, 58] (* Robert G. Wilson v, Mar 29 2016 *) PROG (PARI) a(n) = my(k = 1); while(! ispower(n*k+1, 3), k++); k; \\ Michel Marcus, Mar 30 2016 CROSSREFS Cf. A091733, A266236. Sequence in context: A304947 A013652 A099988 * A138077 A288655 A124192 Adjacent sequences:  A076944 A076945 A076946 * A076948 A076949 A076950 KEYWORD nonn AUTHOR Amarnath Murthy, Oct 20 2002 EXTENSIONS Edited and extended by Robert G. Wilson v, Oct 21 2002 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 September 21 05:55 EDT 2020. Contains 337267 sequences. (Running on oeis4.)