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 A170804 #20 Feb 05 2025 15:08:21 %S A170804 1,2,4,7,11,19,28,44,71,103,167,248,376,619,875,1387,2116,3140,5188, %T A170804 7375,11471,18032,26224,42608,62291,95059,154108,219644,350716,527863, %U A170804 790007,1314295,1845736,2894312,4488635,6585787,10780091,15563060,23951668,38300575 %N A170804 Partial sums of (A006899, prefixed by a 1). %C A170804 a(n) is the minimum number of three-in-a-rows passing through any cell in n-dimensional tic-tac-toe = the minimum value in the n-th row of A352419. - _Ben Orlin_, Mar 22 2022 %o A170804 (Python) %o A170804 from sympy import integer_log %o A170804 def A170804(n): return 1 if n == 1 else ((a:=1<<k+1)<<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())-1 # _Chai Wah Wu_, Feb 05 2025 %Y A170804 Cf. A006899. %Y A170804 Equals A170803 + 1. %Y A170804 Minimum value in the n-th row of A352419. %K A170804 nonn %O A170804 1,2 %A A170804 _N. J. A. Sloane_, Dec 12 2009