OFFSET
1,1
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
FORMULA
a(n) = A078246(n)/n.
MAPLE
f:= proc(n) local q, q2, q5, n1, R, Agenda, d, newA, t, t1, t2;
q2:= padic:-ordp(n, 2);
q5:= padic:-ordp(n, 5);
q:= max(q2, q5);
n1:= n/2^q2/5^q5;
R[7]:= 7: Agenda:= {7}:
if 7 mod n1 = 0 then return 10^q*7/n fi;
for d from 2 do
newA:= NULL;
for t in Agenda do
t1:= 10*t mod n1;
if not assigned(R[t1]) then
R[t1]:= 10*R[t];
newA:= newA, t1;
fi;
t2:= (10*t+7) mod n1;
if t2 = 0 then
return 10^q*(10*R[t]+7)/n;
break
elif not assigned(R[t2]) then
R[t2]:= 10*R[t]+7;
newA:= newA, t2;
fi;
od;
Agenda:= [newA];
od:
end proc:
map(f, [$1..50]); # Robert Israel, Mar 06 2017
MATHEMATICA
f07[n_]:=Module[{k=1}, While[!SubsetQ[{0, 7}, IntegerDigits[n*k]], k++]; k]; Array[f07, 8] (* The program generates the first 8 terms of the sequence. To generate more, increase the Array constant but because some of the terms are quite large the program may take a long time to run. *) (* Harvey P. Dale, Sep 25 2024 *)
CROSSREFS
KEYWORD
AUTHOR
Ray Chandler, Jul 12 2004
STATUS
approved