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%I #14 Feb 13 2017 02:26:05
%S 4,5,7,44,45,47,54,55,57,74,75,77,444,445,447,454,455,457,474,475,477,
%T 544,545,547,554,555,557,574,575,577,744,745,747,754,755,757,774,775,
%U 777,4444,4445,4447,4454,4455,4457,4474,4475,4477,4544,4545,4547,4554,4555,4557,4574,4575,4577,4744
%N Integers whose decimal representation has only digits in {4,5,7}.
%C 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.
%C Exponential density 0.477... = log 3/log 10. - _Charles R Greathouse IV_, Jul 22 2012
%H <a href="/index/Ar#10-automatic">Index entries for 10-automatic sequences</a>.
%Y Cf. A072960 (numbers using only the curved digits 0, 3, 6, 8 and 9).
%K nonn,base,easy
%O 1,1
%A _Jonathan Vos Post_, Jul 21 2012