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

1,1

Links

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

Example

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

Prog

(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

Crossrefs

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

Sequence in context: A066770 A080380 A364278 * A090821 A226575 A052645

Adjacent sequences: A039932 A039933 A039934 * A039936 A039937 A039938

Keyword

base,nonn

Author

Erich Friedman

Extensions

More terms from Patrick De Geest, Oct 15 1999

Status

approved