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 A047894 #34 Mar 17 2025 02:42:45 %S A047894 1,1,2,3,4,6,8,10,12,14,16,19,21,23,26,28,31,34,36,39,42,45,48,51,54, %T A047894 57,60,63,66,69,72,76,79,82,85,89,92,95,99,102,105,109,112,116,119, %U A047894 123,126,130,134,137,141,144,148,152,155,159,163,167,170,174,178,182,185 %N A047894 Number of digits of A000182(n). %D A047894 J. Peters and J. Stein, Mathematische Tafeln. Revised Russian Edition, 1968, Moscow. %H A047894 Amiram Eldar, <a href="/A047894/b047894.txt">Table of n, a(n) for n = 1..10000</a> %F A047894 a(n) = floor(log_10(A000182(n))) + 1. - _Franklin T. Adams-Watters_, Mar 29 2014 %F A047894 a(n) = A055642(A000182(n)). - _Michel Marcus_, Apr 15 2023 %e A047894 a(7) = 8 since the 7th tangential number is 22368256, which has 8 decimal digits. %t A047894 a[n_] := IntegerLength[(2^(2*n)*(2^(2*n) - 1)*Abs[BernoulliB[2*n]])/(2*n)]; Array[a, 100] (* _Amiram Eldar_, Mar 17 2025 after _Stan Wagon_ at A000182 *) %o A047894 (Python) %o A047894 from sympy import bernoulli %o A047894 def A047894(n): return len(str(abs(((2-(2<<(m:=n<<1)))*bernoulli(m)<<m-2)//n))) # _Chai Wah Wu_, Apr 14 2023 %Y A047894 Cf. A000182, A055642, A000384, A034972, A034971, A047893. %K A047894 nonn,base %O A047894 1,3 %A A047894 _Labos Elemer_ %E A047894 a(1) corrected by _Chai Wah Wu_, Apr 14 2023