A214584 Integers whose decimal representation has only digits in {4,5,7}.

4, 5, 7, 44, 45, 47, 54, 55, 57, 74, 75, 77, 444, 445, 447, 454, 455, 457, 474, 475, 477, 544, 545, 547, 554, 555, 557, 574, 575, 577, 744, 745, 747, 754, 755, 757, 774, 775, 777, 4444, 4445, 4447, 4454, 4455, 4457, 4474, 4475, 4477, 4544, 4545, 4547, 4554, 4555, 4557, 4574, 4575, 4577, 4744

Offset: 1

Author

Jonathan Vos Post, Jul 21 2012

Keywords

• nonn
• base
• easy

Comments

These could be called crooked numbers. Integers all of whose numerals are written (san serif) with at least one right or acute angle. The subsequence of crooked primes begins: 5, 7, 47, 457, 547, 557, 577, 757.

Exponential density 0.477... = log 3/log 10. - Charles R Greathouse IV, Jul 22 2012

Links

• Index entries for 10-automatic sequences.

Crossrefs

Cf. A072960 (numbers using only the curved digits 0, 3, 6, 8 and 9).