OFFSET
1,1
COMMENTS
A majority of numbers are divisible by 10.
The case m prime gives A062584 (First occurrence of n in the decimal representation of primes).
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
FORMULA
a(n) = 10*A018800(n) for n >= 9. - Robert Israel, Jun 04 2018
EXAMPLE
a(6) = 603 = 3^2*67 => 603 and 67 start with 6.
MAPLE
with(numtheory): for n from 1 to 47 do: l1:=length(n):i:=0:for m from 2 to 100000 while(i=0) do: x:=factorset(m):k:=nops(x):y:=x[k]: l2:=length(m):x1:=floor(m/(10^(l2-l1))): l3:=length(y):x2:=floor(y/(10^(l3-l1))):if x1=n and x2=n and l2>=l1 and l3 >=l1 and type(m, prime)=false then i:=1: printf(`%d, `, m):else fi :od:od:
# Alternative:
f:= proc(n) local d, k, p;
for d from 1 do
for k from 10^d*n to 10^d*(n+1)-1 do
if not isprime(k) then
p:= max(numtheory:-factorset(k));
if p >= n and floor(p/10^(length(p)-length(n))) = n then return k fi
fi od od
end proc:
map(f, [$1..100]); # Robert Israel, Jun 04 2018
CROSSREFS
KEYWORD
AUTHOR
Michel Lagneau, Oct 18 2011
STATUS
approved