A104426 Numbers k such that the digit 6 does not appear in the decimal expansion of k, Pk, Pk+k, Pk-k, or Pk*k, where Pk is the k-th prime.
1, 3, 4, 7, 8, 9, 10, 11, 12, 13, 20, 21, 22, 25, 30, 33, 35, 37, 41, 43, 44, 48, 50, 51, 52, 53, 54, 55, 58, 70, 72, 75, 80, 81, 82, 83, 85, 93, 95, 128, 149, 152, 170, 171, 174, 184, 185, 187, 188, 189, 194, 198, 201, 203, 210, 212, 215, 217, 233, 235, 238, 242, 245
Offset: 1
Crossrefs
Programs
-
Mathematica
id[x_]:=IntegerDigits[x];pr[i_]:=Prime[i];ra=Range[3000];A104426=Select[ra, Position[Union[id[ # ], id[pr[ # ]], id[pr[ # ]+# ], id[pr[ # ]-# ], id[pr[ # ]*# ]], 6]=={}&] slQ[n_]:=Module[{p=Prime[n]},Union[DigitCount[#,10,6]&/@{n,p,p+n,p-n, p*n}] == {0}]; Select[Range[250],slQ] (* Harvey P. Dale, Feb 01 2018 *)
-
PARI
has(n)=!setsearch(Set(digits(n)),6) is(n,p=prime(n))=has(n) && has(p) && has(p+n) && has(p-n) && has(p*n) \\ Charles R Greathouse IV, Feb 01 2018
Extensions
Definition modified (at the suggestion of N. J. A. Sloane) by Harvey P. Dale, Feb 10 2018
Comments