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A028373 Numbers that have only the straight digits {1, 4, 7}. 12
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 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
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 *)
PROG
(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
CROSSREFS
Cf. A028374, the curved sequence.
Cf. A079651 prime numbers using only the straight digits 1,4,7.
Sequence in context: A184623 A184581 A310725 * A310726 A310727 A190769
KEYWORD
easy,nonn,base
AUTHOR
Greg Heil (gheil(AT)scn.org), Dec 11 1999
STATUS
approved

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Last modified May 20 23:09 EDT 2024. Contains 372720 sequences. (Running on oeis4.)