OFFSET
1,1
COMMENTS
From Seiichi Manyama, Aug 22 2017: (Start)
For k >= 1, (10^(6*k) - 1)/7 is a term.
For 5 <= a <= 9 and k >= 1, a*(10^(42*k) - 1)/49 is a term. (End)
LINKS
Robert Israel, Table of n, a(n) for n = 1..258
Wikipedia, Parasitic number.
EXAMPLE
From Seiichi Manyama, Aug 22 2017: (Start)
b1 = 14285.
a(1) = b1*10 + 7,
5*a(1) = 714285 = 7*10^5 + b1.
b7 = 10204081632653061224489795918367346938775.
a(7) = b7*10 + 5,
5*a(7) = 510204081632653061224489795918367346938775 = 5*10^41 + b7. (End)
MAPLE
f:= proc(d) # solutions with d+1 digits
local b, R, a;
R:= NULL;
for b from ceil(49*10^(d-1)/(10^d - 1)) to 9 do
a:= (10^d-5)*b/49;
if a::integer then R:= R, 10*a+b fi
od;
R
end proc:
map(f, [$1..42]); # Robert Israel, Nov 05 2024
CROSSREFS
KEYWORD
nonn,base
AUTHOR
N. J. A. Sloane, based on correspondence from William A. Hoffman III (whoff(AT)robill.com), Apr 10 2009
STATUS
approved