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

1,1

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

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Index entries for 10-automatic sequences.

Mathematica

Table[FromDigits/@Tuples[{4, 5, 7}, d], {d, 4}]//Flatten (* Harvey P. Dale, Jun 12 2026 *)

Crossrefs

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

Sequence in context: A123368 A292164 A178439 * A198131 A200387 A152974

Adjacent sequences: A214581 A214582 A214583 * A214585 A214586 A214587

Keyword

nonn,base,easy,changed

Author

Jonathan Vos Post, Jul 21 2012

Status

approved