A078239 a(n) = smallest multiple of n using only prime digits, with a(n) = 0 if there are none.

2, 2, 3, 32, 5, 72, 7, 32, 27, 0, 22, 72, 52, 252, 75, 32, 255, 72, 57, 0, 252, 22, 23, 72, 25, 52, 27, 252, 232, 0, 372, 32, 33, 272, 35, 72, 37, 532, 273, 0, 533, 252, 2322, 352, 225, 322, 235, 2352, 735, 0, 255, 52, 53, 2322, 55, 2352, 57, 232, 2537, 0, 732, 372, 252, 2752, 325, 2772, 335, 272

Offset: 1

Author

Amarnath Murthy, Nov 23 2002

Keywords

• base
• easy
• nonn

Comments

Besides multiples of 10, 625 and its odd multiples have a(n)=0. - Robert Israel, Feb 12 2018

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Programs

Maple

f := proc (n) local k, k10, j;
  if n mod 10 = 0 or n mod 625 = 0 then return 0 end if;
  k10 := select(t -> member(t*n mod 10, {2, 3, 5, 7}), [$1 .. 9]);
  for j from 0 do
    for k in k10 do
      if convert(convert((10*j+k)*n, base, 10), set) subset {2, 3, 5, 7}
      then return (10*j+k)*n
      fi
od od
end proc:
map(f, [$1..100]; # Robert Israel, Feb 12 2018

Extensions

Edited and more terms from Robert Israel, Feb 12 2018