A029554 Quasi-Carmichael numbers to base 9: squarefree composites n such that (n,2*3*5*7) = 1 and prime p|n ==> p-9|n-9.

209, 6409, 9361, 11713, 12749, 19721, 21593, 32509, 50609, 74269, 85289, 88559, 91793, 99199, 100529, 152329, 167977, 187889, 235049, 271469, 313049, 471977, 742729, 828529, 841033, 925129, 1057793, 1078649, 1186949, 1265609, 1324609

Offset: 1

Author

David W. Wilson

Keywords

• nonn

Comments

If multiples of 2, 3, 5 and 7 are not excluded, then terms like 21, 33, 65, 77, 105, 165, 231,... belong to the sequence. - Giovanni Resta, May 21 2013

Links

• Giovanni Resta, Table of n, a(n) for n = 1..2091 (terms < 10^12)
• Index entries for sequences related to Carmichael numbers.

Programs

Mathematica

qcm[n_, d_] := Block[{p, e}, {p, e} = Transpose@FactorInteger@n; Length[p] > 1 && Max[e] == 1 && d < Min[p] && And @@ IntegerQ /@ ((n - d)/(p - d))]; Select[Range[10^6], qcm[#, 9] &] (* Giovanni Resta, May 21 2013 *)