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A265525 a(n) = largest base-10 palindrome m <= n such that every base-10 digit of m is <= the corresponding digit of n. 1
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 11, 11, 11, 11, 11, 11, 11, 11, 11, 0, 11, 22, 22, 22, 22, 22, 22, 22, 22, 0, 11, 22, 33, 33, 33, 33, 33, 33, 33, 0, 11, 22, 33, 44, 44, 44, 44, 44, 44, 0, 11, 22, 33, 44, 55, 55, 55, 55, 55, 0, 11, 22, 33, 44, 55, 66, 66, 66, 66, 0, 11, 22, 33, 44, 55, 66, 77, 77, 77, 0, 11, 22, 33 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 0..9999

MAPLE

ispal := proc(n) # test for base-b palindrome

local L, Ln, i;

global b;

L := convert(n, base, b);

Ln := nops(L);

for i to floor(1/2*Ln) do

if L[i] <> L[Ln + 1 - i] then return false end if

end do;

return true

end proc

# find max pal <= n and in base-b shadow of n, write in base 10

under10:=proc(n) global b;

local t1, t2, i, m, sw1, L2;

if n mod b = 0 then return(0); fi;

t1:=convert(n, base, b);

for m from n by -1 to 0 do

if ispal(m) then

t2:=convert(m, base, b);

L2:=nops(t2);

sw1:=1;

for i from 1 to L2 do

if t2[i] > t1[i] then sw1:=-1; break; fi;

od:

if sw1=1 then return(m); fi;

fi;

od;

end proc;

b:=10; [seq(under10(n), n=0..144)]; # Gives A265525

PROG

(Haskell)

a265525 n = a265525_list !! n

a265525_list = f a031298_tabf [[]] where

   f (ds:dss) pss = y : f dss pss' where

     y = foldr (\d v -> 10 * v + d) 0 ys

     (ys:_) = dropWhile (\ps -> not $ and $ zipWith (<=) ps ds) pss'

     pss' = if ds /= reverse ds then pss else ds : pss

-- Reinhard Zumkeller, Dec 11 2015

CROSSREFS

Sequences related to palindromic floor and ceiling: A175298, A206913, A206914, A261423, A262038, and the large block of consecutive sequences beginning at A265509.

Cf. A002113, A031298.

Sequence in context: A139281 A059707 A256754 * A056967 A321243 A067079

Adjacent sequences:  A265522 A265523 A265524 * A265526 A265527 A265528

KEYWORD

nonn,base,look

AUTHOR

N. J. A. Sloane, Dec 09 2015

STATUS

approved

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Last modified September 17 12:57 EDT 2019. Contains 327131 sequences. (Running on oeis4.)