This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A170805 #9 Feb 05 2025 16:18:56 %S A170805 1,2,3,5,8,12,20,29,45,72,104,168,249,377,620,876,1388,2117,3141,5189, %T A170805 7376,11472,18033,26225,42609,62292,95060,154109,219645,350717,527864, %U A170805 790008,1314296,1845737,2894313,4488636,6585788,10780092,15563061,23951669,38300576 %N A170805 a(n) = A170803(n-1) + 2, with a(0) = 1, a(1) = 2. %H A170805 Boris Alexeev, <a href="https://arxiv.org/abs/cs/0309052">Minimal DFAs for testing divisibility</a>, arXiv:cs/0309052 [cs.CC], 2003. %o A170805 (Python) %o A170805 from sympy import integer_log %o A170805 def A170805(n): return n+1 if n<2 else ((a:=1<<k+1)<<1)+(3**integer_log(a,3)[0]*3-1>>1) if 6**(k:=integer_log(m:=3**(n-2),6)[0])<<1<m else ((a:=3**integer_log(1<<n-1,6)[0])*3-1>>1)+(1<<a.bit_length()) # _Chai Wah Wu_, Feb 05 2025 %Y A170805 Cf. A170803. %K A170805 nonn %O A170805 0,2 %A A170805 _N. J. A. Sloane_, Dec 12 2009