OFFSET
1,1
COMMENTS
It appears that the largest terms occur when n=1 mod 9 and moderately large terms when n=4 or 7 mod 9.
LINKS
Giovanni Resta, Table of n, a(n) for n = 1..10000
EXAMPLE
a(13)=3 since the only three solutions are 117=9*13, 156=12*13 and 195=15*13.
MAPLE
read("transforms"):
A037478 := proc(n)
local a, x, k;
a := 0 ;
for k from 1 do
x := n*k ;
if digsum(x)*n = x then
a := a+1 ;
end if;
# may stop if x/digsum(x)>n, so if x/#digits(x) > 9*n
if x/A055642(x) > 9*n then
break;
end if;
end do:
a ;
end proc:
seq(A037478(n), n=1..101) ; # R. J. Mathar, May 11 2016
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Henry Bottomley, Sep 12 2000
STATUS
approved