A242742 Let k be the n-th composite number: then a(n) is the smallest base b such that b^(k-1) == 1 (mod k).

5, 7, 9, 8, 11, 13, 15, 4, 17, 19, 21, 8, 23, 25, 7, 27, 26, 9, 31, 33, 10, 35, 6, 37, 39, 14, 41, 43, 45, 8, 47, 49, 18, 51, 16, 9, 55, 21, 57, 20, 59, 61, 63, 8, 65, 8, 25, 69, 22, 11, 73, 75, 26, 45, 34, 79, 81, 80, 83, 85, 4, 87, 28, 89, 91, 3, 93, 32, 95

Offset

1,1

Links

Felix Fröhlich, Table of n, a(n) for n = 1..8769 (all terms up to k=10^4)

Formula

a(n) = A105222(A002808(n)). - Michel Marcus, Aug 21 2014

Mathematica

sbb[n_]:=Module[{b=2}, While[PowerMod[b, n-1, n]!=1, b++]; b]; sbb/@Select[ Range[ 100], CompositeQ] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Dec 29 2018 *)

Prog

(PARI) forcomposite(k=2, 1e2, for(b=2, 1e9, if(Mod(b, k)^(k-1)==1, print1(b, ", "); next({2}))); print1(">1e9, "))

Crossrefs

Cf. A002808, A001567, A105222, A181780, A211455, A211456, A211457, A211458.

Sequence in context: A308713 A109352 A228578 * A323602 A164029 A364681

Adjacent sequences: A242739 A242740 A242741 * A242743 A242744 A242745

Keyword

nonn

Author

Felix Fröhlich, Aug 16 2014

Status

approved