OFFSET
1,1
COMMENTS
For odd n not a multiple of 5, a(n) is not 0, as every such odd number divides a (infinitely many) unary number of the type 11111...= (10^k-1)/9, by Fermat's little theorem. E.g., 13 divides 111111, hence a(13) = 111111333333. Zeros occur only for some powers/multiples of 2 and 5 as 25 does not divide 222555... etc. and 16 cannot divide any number of the type 111...666...
REFERENCES
Amarnath Murthy, On the divisors of unary sequence, Smarandache Notions Journal, Vol-11, 2000.
LINKS
Robert Israel, Table of n, a(n) for n = 1..360
MAPLE
f:= proc(n) local x, L, i, m, eq, S;
L:= convert(n, base, 10);
eq:= add(L[i]*10^(i*m)*(1-10^(-m))/9, i=1..nops(L));
S:= map(t -> rhs(op(t)), {msolve(eq, n)}) minus {0, 1};
if S = {} then 0
elif S = {m} then eval(eq, m=2)
else eval(eq, m = min(S))
fi
end proc:
map(f, [$1..30]); # Robert Israel, Aug 18 2024
CROSSREFS
KEYWORD
base,easy,nonn
AUTHOR
Amarnath Murthy, Aug 09 2005
EXTENSIONS
More terms from Franklin T. Adams-Watters, Jun 06 2006
STATUS
approved