OFFSET
1,2
COMMENTS
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
EXAMPLE
All divisors of 1859 (1, 11, 13, 169, 1859) start with digit 1.
MAPLE
fd1:= n -> n < 2*10^ilog10(n):
filter:= proc(n) not isprime(n) and andmap(fd1, numtheory:-divisors(n)) end proc:
select(filter, [1, seq(seq(i, i=10^d+1..2*10^d-1, 2), d=1..3)]); # Robert Israel, Mar 13 2019
MATHEMATICA
fQ[n_] := Module[{d = Divisors[n]}, Union[IntegerDigits[#][[1]] & /@ d] == {1}]; Select[Range[1991], ! PrimeQ[#] && fQ[#] &] (* T. D. Noe, Feb 13 2012 *)
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Jaroslav Krizek, Feb 12 2012
STATUS
approved