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 A081394 #13 May 15 2023 08:46:37 %S A081394 1,6,10,27,96,147,363,627,959,1547,1919,2641,2645,3339,6241,6909,6913, %T A081394 6943,6923,6937,16405,19981,24325,31675,31679,35329,36959,36963,38915, %U A081394 38927,73563,39729,73577,80095,87205,87309,95035,123307,123305,123369,123367,174239,185915,186361,186369,186373,186381 %N A081394 a(n) is the smallest k such that number of non-unitary prime divisors of central binomial coefficient, A001405(k) = C(k, floor(k/2)) equals n. %F A081394 a(n) = Min{k; A056175(k) = n}. %e A081394 n=8: a(8)=959, C(959,479) has 8 non-unitary prime divisors: {2,3,5,7,11,13,23,29} and 959 is the smallest. %t A081394 seq[len_, kmax_] := Module[{s = Table[0, {len}], k = 1, c = 0, i}, While[c < len && k < kmax, i = Count[FactorInteger[Binomial[k, Floor[k/2]]][[;; , 2]], _?(# > 1 &)] + 1; If[i <= len && s[[i]] == 0, c++; s[[i]] = k]; k++]; TakeWhile[s, # > 0 &]]; seq[20, 10^4] (* _Amiram Eldar_, May 15 2023 *) %Y A081394 Cf. A081387, A081393, A081395, A056175. %K A081394 nonn %O A081394 0,2 %A A081394 _Labos Elemer_, Mar 27 2003 %E A081394 a(9)-a(19) from _Michel Marcus_, Sep 01 2019 %E A081394 a(20)-a(46) from _Amiram Eldar_, May 15 2023