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!)
 A259230 a(n) = smallest k such that (A115091(n)-k)! == -1 (mod A115091(n)^2). 1
 1, 6, 1, 24, 64, 1, 384 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS The values of m in A115091. A115091(n) is in A007540 iff a(n) = 1. LINKS EXAMPLE a(2) = 6, because 6 is the smallest k such that (A115091(2)-k)! == -1 (mod A115091(2)^2), which yields the congruence (11-6)! == -1 (mod 11^2). MATHEMATICA t = Select[Prime@ Range@ 120, AnyTrue[Range@ #, Function[m, Divisible[m! + 1, #^2]]] &]; Table[k = 1; While[Mod[(t[[n]] - k)!, t[[n]]^2] != t[[n]]^2 - 1, k++]; k, {n, 7}] (* Michael De Vlieger, Nov 10 2015, Version 10 *) PROG (PARI) forprime(p=1, , for(k=1, p-1, if(Mod((p-k)!, p^2)==-1, print1(k, ", "); break({1})))) CROSSREFS Cf. A007540, A115091. Sequence in context: A338865 A278958 A281631 * A278756 A147327 A145629 Adjacent sequences:  A259227 A259228 A259229 * A259231 A259232 A259233 KEYWORD nonn,hard,more AUTHOR Felix Fröhlich, Nov 08 2015 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 07:28 EDT 2021. Contains 347596 sequences. (Running on oeis4.)