cp's OEIS Frontend

A217394 Numbers starting with 2.

%I A217394 #42 Dec 07 2024 11:10:11
%S A217394 2,20,21,22,23,24,25,26,27,28,29,200,201,202,203,204,205,206,207,208,
%T A217394 209,210,211,212,213,214,215,216,217,218,219,220,221,222,223,224,225,
%U A217394 226,227,228,229,230,231,232,233,234,235,236,237,238,239,240,241,242
%N A217394 Numbers starting with 2.
%C A217394 The lower and upper asymptotic densities of this sequence are 1/18 and 10/27, respectively. - _Amiram Eldar_, Feb 27 2021
%H A217394 Jeremy Gardiner, <a href="/A217394/b217394.txt">Table of n, a(n) for n = 1..1111</a>
%H A217394 <a href="/index/Ar#10-automatic">Index entries for 10-automatic sequences</a>.
%F A217394 a(n) = n + (17*10^floor(log_10(9*n-8))-8)/9. - _Alan Michael Gómez Calderón_, May 15 2023
%t A217394 Select[Range[300], IntegerDigits[#][[1]] == 2 &] (* _T. D. Noe_, Oct 02 2012 *)
%o A217394 (Python)
%o A217394 def agen():
%o A217394   yield 2
%o A217394   digits, adder = 1, 20
%o A217394   while True:
%o A217394     for i in range(10**digits): yield adder + i
%o A217394     digits, adder = digits+1, adder*10
%o A217394 g = agen()
%o A217394 print([next(g) for i in range(54)]) # _Michael S. Branicky_, Feb 20 2021
%o A217394 (Python)
%o A217394 def A217394(n): return n+(17*10**(len(str(9*n-8))-1))//9 # _Chai Wah Wu_, Dec 07 2024
%Y A217394 Cf. A006092, A011532.
%Y A217394 Subsequences include: A045708, A045726, A077327, A077678, A106412, A106422.
%Y A217394 Cf. A131835, A217395, A217397, A217398, A217399, A217400, A217401, A217402.
%K A217394 nonn,base,easy
%O A217394 1,1
%A A217394 _Jeremy Gardiner_, Oct 02 2012