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!)
 A263239 Euler pseudoprimes to base 9: composite integers such that abs(9^((n - 1)/2)) == 1 mod n. 1
 4, 28, 91, 121, 286, 532, 671, 703, 949, 1036, 1105, 1541, 1729, 1891, 2465, 2665, 2701, 2821, 3281, 3367, 3751, 4636, 4961, 5551, 6364, 6601, 7381, 8401, 8911, 10585, 11011, 11476, 12403, 14383, 15203, 15457, 15841, 16471, 16531, 18721, 19345, 19684, 23521, 24046, 24661, 24727 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Even numbers are permitted since 9 is an integer square. - Charles R Greathouse IV, Oct 12 2015 LINKS Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..116 from Daniel Lignon) MATHEMATICA eulerPseudo9Q[n_]:=(Mod[9^((n-1)/2)+1, n]==0 ||Mod[9^((n-1)/2)-1, n]==0) && Not[PrimeQ[n]]; Select[Range[2, 200000], eulerPseudo9Q] PROG (PARI) is(n) = abs(centerlift(Mod(3, n)^(n-1)))==1 && !isprime(n) && n>1 \\ Charles R Greathouse IV, Oct 12 2015 CROSSREFS Cf. A020138 (pseudoprimes to base 9). Cf. A006970 (base 2), A262051 (base 3), A262052 (base 5), A262053 (base 6), A262054 (base 7), A262055 (base 8). Sequence in context: A183485 A183437 A294315 * A296015 A187452 A173296 Adjacent sequences:  A263236 A263237 A263238 * A263240 A263241 A263242 KEYWORD nonn AUTHOR Daniel Lignon, Oct 12 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 23 20:42 EDT 2021. Contains 347617 sequences. (Running on oeis4.)