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 A028373 Numbers that have only the straight digits {1, 4, 7}. 12

%I #17 Jul 25 2015 12:53:29

%S 1,4,7,11,14,17,41,44,47,71,74,77,111,114,117,141,144,147,171,174,177,

%T 411,414,417,441,444,447,471,474,477,711,714,717,741,744,747,771,774,

%U 777,1111,1114,1117,1141,1144,1147,1171,1174,1177,1411,1414,1417,1441

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

%H Alois P. Heinz, <a href="/A028373/b028373.txt">Table of n, a(n) for n = 1..1000</a>

%p a:= proc(n) local d, i, m, r; m:=n; r:=0;

%p for i from 0 while m>0 do

%p d:= irem(m, 3, 'm');

%p if d=0 then d:=3; m:=m-1 fi;

%p r:= r+10^i*[1, 4, 7][d]

%p od: r

%p end:

%p seq(a(n), n=1..100); # _Alois P. Heinz_, May 25 2014

%t f[n_] := Block[{id = IntegerDigits[n], straight = {1, 4, 7}}, If[ Union[ Join[id, straight]] == straight, True, False]]; Select[ Range[0, 1446], f[ # ] & ]

%t FromDigits/@Flatten[Table[Tuples[{1,4,7},n],{n,4}],1] (* _Harvey P. Dale_, Jul 25 2015 *)

%o (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

%Y Cf. A028374, the curved sequence.

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

%K easy,nonn,base

%O 1,2

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

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Last modified June 24 00:53 EDT 2024. Contains 373661 sequences. (Running on oeis4.)