A087995 Base-10 palindromes that cannot be formed by performing reverse-and-add operations on any previous nonpalindromic positive integers.

0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 111, 131, 151, 171, 191, 212, 232, 252, 272, 292, 313, 333, 353, 373, 393, 414, 434, 454, 474, 494, 515, 535, 555, 575, 595, 616, 636, 656, 676, 696, 717, 737, 757, 777, 797, 818, 838, 858, 878, 898, 919, 939, 959, 979, 999

Offset

1,3

Links

Table of n, a(n) for n=1..55.

Example

a(11) = 111 because 111 cannot be produced by performing reverse-and-add operations on any number prior to 111 that is not already a palindrome.

Maple

reverse := proc (d) local n, m; m := 0; n := d; while n>0 do m := m*10+(n mod 10); n := (n-(n mod 10))/10; od; m; end; isPalindromic := proc (n) if (n=reverse(n)) then true; else false; fi; end; revAddPal := proc (n) local m, i; i := 0; m := n; while not(isPalindromic(m)) and (i<10^2) do i := i+1; m := m+reverse(m); od; isPalindromic(m), m, i; end; revAddPalSeq2 := proc(numTerms) local i, sPals, allPals, r; sPals := {}; allPals := {}; for i from 0 to numTerms do if not(isPalindromic(i)) then r := [revAddPal(i)]; if r[1] then sPals := sPals union {r[2]}; fi; else allPals := allPals union {i}; fi; od; allPals minus sPals; end; revAddPalSeq2(1000);

Crossrefs

Sequence in context: A056143 A106003 A283868 * A082232 A117228 A032567

Adjacent sequences: A087992 A087993 A087994 * A087996 A087997 A087998

Keyword

base,nonn

Author

Chuck Seggelin (barkeep(AT)plastereddragon.com), Oct 28 2003

Status

approved