A213879 Positive palindromes that are not the sum of two positive palindromes.

1, 111, 131, 141, 151, 161, 171, 181, 191, 1331, 1441, 1551, 1661, 1771, 1881, 1991, 10301, 10401, 10501, 10601, 10701, 10801, 10901, 11111, 11211, 11311, 11411, 11511, 11611, 11711, 11811, 11911, 12021, 12121, 12321, 12421, 12521, 12621, 12721, 12821

Offset

1,2

Comments

These numbers do not occur in A035137.

Links

Alois P. Heinz, Table of n, a(n) for n = 1..2151 (first 111 terms from N. J. A. Sloane)

Eric Weisstein's World of Mathematics, Palindromic Number

Index entries for sequences related to palindromes

Formula

({ A002113 } intersect { A319477 }) minus { 0 }. - Alois P. Heinz, Sep 19 2018

Example

22 is not a member because 22 = 11 + 11.

Maple

# From N. J. A. Sloane, Sep 09 2015: bP is a list of the palindromes
a:={}; M:=400; for n from 3 to M do p:=bP[n];
# is p a sum of two palindromes?
sw:=-1; for i from 2 to n-1 do j:=p-bP[i]; if digrev(j)=j then sw:=1; break; fi;
od;
if sw<0 then a:={op(a), p}; fi; od:
b:=sort(convert(a, list));

Mathematica

lst1 = {}; lst2 = {}; r = 12821; Do[If[FromDigits@Reverse@IntegerDigits[n] == n, AppendTo[lst1, n]], {n, r}]; l = Length[lst1]; Do[s = lst1[[i]] + lst1[[j]]; AppendTo[lst2, s], {i, l - 1}, {j, i}]; Complement[lst1, lst2]
palQ[n_] := Reverse[x = IntegerDigits[n]] == x; t1 = Select[Range[12900], palQ[#] &]; Complement[t1, Union[Flatten[Table[i + j, {i, t1}, {j, t1}]]]] (* Jayanta Basu, Jun 15 2013 *)

Crossrefs

Cf. A002113, A014092, A035137, A083142, A088601, A260255, A319477.

Sequence in context: A070798 A235039 A279423 * A095613 A108721 A084325

Adjacent sequences: A213876 A213877 A213878 * A213880 A213881 A213882

Keyword

base,nonn

Author

Arkadiusz Wesolowski, Jun 23 2012

Status

approved