cp's OEIS Frontend

A261906 Numbers that are the sum of two nonzero palindromes.

%I A261906 #10 Apr 27 2025 10:55:58
%S A261906 2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,22,23,24,25,26,27,
%T A261906 28,29,30,31,33,34,35,36,37,38,39,40,41,42,44,45,46,47,48,49,50,51,52,
%U A261906 53,55,56,57,58,59,60,61,62,63,64,66,67,68,69,70,71,72,73,74,75,77,78,79,80,81,82,83,84,85,86,88,89,90,91,92,93,94,95,96,97,99,100,101,102,103,104,105,106,107,108,109,110,112,113,114,115,116,117,118,119,120
%N A261906 Numbers that are the sum of two nonzero palindromes.
%C A261906 More than the usual number of terms are shown in order to distinguish this from A260255.
%e A261906 22 is a member because it is the sum of two palindromes, 11+11 (not because it is a palindrome in its own right).
%e A261906 111 is not the sum of two nonzero palindromes, so appears in A260255 but not here. See A213879 for further differences between the two sequences.
%p A261906 # Sums of two nonzero pals:
%p A261906 # bP has a list of palindromes starting at 0.
%p A261906 a2:={}; M:=60; M2:=bP[M];
%p A261906 for i from 2 to M do
%p A261906 for j from i to M do
%p A261906 k:=bP[i]+bP[j];
%p A261906 if k <= M2 then a2:={op(a2),k}; fi;
%p A261906 od: od:
%p A261906 b2:=sort(convert(a2,list));
%t A261906 Take[Total/@Tuples[Select[Range[200],PalindromeQ],2]//Union,120] (* _Harvey P. Dale_, Apr 27 2025 *)
%Y A261906 Cf. A002113, A260255, A213879.
%K A261906 nonn,base
%O A261906 1,1
%A A261906 _N. J. A. Sloane_, Sep 09 2015