A217397 - OEIS

%I #22 Dec 07 2024 11:11:06

%S 4,40,41,42,43,44,45,46,47,48,49,400,401,402,403,404,405,406,407,408,

%T 409,410,411,412,413,414,415,416,417,418,419,420,421,422,423,424,425,

%U 426,427,428,429,430,431,432,433,434,435,436,437,438,439,440,441,442

%N Numbers starting with 4.

%C The lower and upper asymptotic densities of this sequence are 1/36 and 2/9, respectively. - _Amiram Eldar_, Feb 27 2021

%H Jeremy Gardiner, <a href="/A217397/b217397.txt">Table of n, a(n) for n = 1..1111</a>

%H <a href="/index/Ar#10-automatic">Index entries for 10-automatic sequences</a>.

%F a(n) = n + (35*10^floor(log_10(9*n-8))-8)/9. - _Alan Michael Gómez Calderón_, May 17 2023

%t Select[Range[1000], IntegerDigits[#][[1]] == 4 &] (* _T. D. Noe_, Oct 02 2012 *)

%o (Python)

%o def A217397(n): return n+(35*10**(len(str(9*n-8))-1))//9 # _Chai Wah Wu_, Dec 07 2024

%Y Cf. A000867, A011534.

%Y Subsequences include: A045710, A077329, A077680, A106414, A106424.

%Y Cf. A131835, A217394, A217395, A217398, A217399, A217400, A217401, A217402.

%K nonn,base,easy

%O 1,1

%A _Jeremy Gardiner_, Oct 02 2012