A028373 Numbers that have only the straight digits {1, 4, 7}.

1, 4, 7, 11, 14, 17, 41, 44, 47, 71, 74, 77, 111, 114, 117, 141, 144, 147, 171, 174, 177, 411, 414, 417, 441, 444, 447, 471, 474, 477, 711, 714, 717, 741, 744, 747, 771, 774, 777, 1111, 1114, 1117, 1141, 1144, 1147, 1171, 1174, 1177, 1411, 1414, 1417, 1441

Offset: 1

Author

Greg Heil (gheil(AT)scn.org), Dec 11 1999

Keywords

• easy
• nonn
• base

Links

• Alois P. Heinz, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A028374, the curved sequence.

Cf. A079651 prime numbers using only the straight digits 1,4,7.

Programs

Maple

a:= proc(n) local d, i, m, r; m:=n; r:=0;
      for i from 0 while m>0 do
        d:= irem(m, 3, 'm');
        if d=0 then d:=3; m:=m-1 fi;
        r:= r+10^i*[1, 4, 7][d]
      od: r
    end:
seq(a(n), n=1..100);  # Alois P. Heinz, May 25 2014

Mathematica

f[n_] := Block[{id = IntegerDigits[n], straight = {1, 4, 7}}, If[ Union[ Join[id, straight]] == straight, True, False]]; Select[ Range[0, 1446], f[ # ] & ]
FromDigits/@Flatten[Table[Tuples[{1,4,7},n],{n,4}],1] (* Harvey P. Dale, Jul 25 2015 *)

PARI

is(n)=my(t);while(n,t=n%10;if(t!=1&&t!=4&&t!=7,return(0));n\=10);!!t \\ Charles R Greathouse IV, Sep 25 2012