cp's OEIS Frontend

A261914 Largest palindrome < n (or 0 if n=0).

%I A261914 #13 Oct 17 2022 10:49:48
%S A261914 0,0,1,2,3,4,5,6,7,8,9,9,11,11,11,11,11,11,11,11,11,11,11,22,22,22,22,
%T A261914 22,22,22,22,22,22,22,33,33,33,33,33,33,33,33,33,33,33,44,44,44,44,44,
%U A261914 44,44,44,44,44,44,55,55,55,55,55,55,55,55,55,55,55
%N A261914 Largest palindrome < n (or 0 if n=0).
%H A261914 N. J. A. Sloane, <a href="/A261914/b261914.txt">Table of n, a(n) for n = 0..20000</a>
%H A261914 <a href="/index/Pac#palindromes">Index entries for sequences related to palindromes</a>
%F A261914 a(n) = A261423(n-1) for all n>0. - _M. F. Hasler_, Sep 11 2015
%p A261914 # Pal has list of palindromes; palfloor is A261423
%p A261914 palfloor:=proc(n) global Pal; local i;
%p A261914 for i from 1 to nops(Pal) do
%p A261914    if Pal[i]=n then return(n); fi;
%p A261914    if Pal[i]>n then return(Pal[i-1]); fi;
%p A261914 od:
%p A261914 end;
%p A261914 prevpal:=proc(n) global palfloor;
%p A261914 if n=0 then return(0);
%p A261914 elif member(n,Pal) then return(palfloor(n-1));
%p A261914 else return(palfloor(n)); fi; end;
%t A261914 lp[n_]:=Module[{k=n-1},While[!PalindromeQ[k],k--];k]; Join[{0},Array[lp,70]] (* _Harvey P. Dale_, Oct 17 2022 *)
%o A261914 (Haskell)
%o A261914 a261914 n = a261914_list !! n
%o A261914 a261914_list = f 0 a002113_list where
%o A261914    f n ps@(p:ps'@(p':_)) = p : f (n + 1) (if n < p' then ps else ps')
%o A261914 -- _Reinhard Zumkeller_, Sep 16 2015
%Y A261914 Similar to but of course different from A261423.
%K A261914 nonn,base
%O A261914 0,4
%A A261914 _N. J. A. Sloane_, Sep 10 2015