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 A131841 #15 Mar 01 2025 17:44:31 %S A131841 0,0,1,1,2,2,2,2,2,2,2,2,2,3,3,2,2,2,3,2,2,2,2,2,3,2,2,2,2,3,2,3,3,3, %T A131841 3,2,3,2,2,2,3,3,3,3,3,2,2,3,3,3,3,3,3,2,3,2,3,2,3,3,3,3,3,3,3,2,2,3, %U A131841 2,2,3,3,3,2,2,2,2,2,3,2,2,2,3,3,2,3,3,3 %N A131841 Additive persistence of Woodall numbers. %F A131841 a(n) = A031286(A003261(n)). - _James C. McMahon_, Mar 01 2025 %e A131841 Woodall number 159 --> 1+5+9=15 --> 1+5=6 thus persistence is 2 %p A131841 with(numtheory): with(combinat): P:=proc(n) local a,t;t:=0; a:=n*2^n-1; while a>9 do t:=t+1; a:=convert(convert(a,base,10),`+`); od; t; %p A131841 end: seq(P(i),i=1..10^2); %t A131841 f[n_] := Length@ NestWhileList[Plus @@ IntegerDigits@# &, n*2^n - 1, UnsameQ@## &, All] - 2; Array[f, 88] (* _James C. McMahon_, Mar 01 2025 *) %Y A131841 Cf. A003261, A031286, A131838. %K A131841 easy,nonn,base %O A131841 1,5 %A A131841 _Paolo P. Lava_ and _Giorgio Balzarotti_, Jul 20 2007 %E A131841 Corrected entries and Maple code by _Paolo P. Lava_, Dec 19 2017