A039935 Smallest k for which k, 2k, ... nk all contain the digit 4.

4, 24, 47, 471, 487, 1248, 1249, 6248, 6249, 6249, 12493, 12493, 12493, 12493, 12498, 31249, 62499, 62499, 62499, 62499, 62499, 62499, 62499, 62499, 62499, 62499, 62499, 62499, 62499, 62499, 62499, 312497, 312497, 312497, 624984, 624984, 624984, 624984, 624984

Offset: 1

Author

Erich Friedman

Keywords

• base
• nonn

Examples

			a(3) = 47 since 47, 94 and 141 all contain a 4.
		

Links

• Giovanni Resta, Table of n, a(n) for n = 1..2047

Crossrefs

Cf. A039932, A039933, A039934, A039936, A039937, A039938, A039939, A039940.

Programs

Python

def aupton(terms):
  k, n, alst = 1, 1, []
  while len(alst) < terms:
    while not all(str(i*k).count('4') > 0 for i in range(1, n+1)): k += 1
    while str(n*k).count('4') > 0: alst.append(k); n += 1
    k += 1
  return alst[:terms]
print(aupton(39)) # Michael S. Branicky, Apr 24 2021

Extensions

More terms from Patrick De Geest, Oct 15 1999