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A347401 Lexicographically earliest sequence of distinct terms > 0 such that the sum n + a(n) forms a palindrome in base 10.

%I A347401 #7 Aug 30 2021 21:48:57
%S A347401 1,2,3,4,6,5,15,14,13,12,11,10,9,8,7,17,16,26,25,24,23,22,21,20,19,18,
%T A347401 28,27,37,36,35,34,33,32,31,30,29,39,38,48,47,46,45,44,43,42,41,40,50,
%U A347401 49,60,59,58,57,56,55,54,53,52,51,70,69,68,67,66,65,64,63,62,61,80,79,78,77,76,75,74,73
%N A347401 Lexicographically earliest sequence of distinct terms > 0 such that the sum n + a(n) forms a palindrome in base 10.
%e A347401 For n = 4 we have a(4) = 4 and 4 + 4 = 8 is a palindrome in base 10;
%e A347401 for n = 5 we have a(5) = 6 and 5 + 6 = 11 is a palindrome in base 10;
%e A347401 for n = 6 we have a(6) = 5 and 6 + 5 = 11 is a palindrome in base 10;
%e A347401 for n = 7 we have a(7) = 15 and 7 + 15 = 22 is a palindrome in base 10;
%e A347401 for n = 8 we have a(8) = 14 and 8 + 14 = 22 is a palindrome in base 10; etc.
%o A347401 (Python)
%o A347401 def ispal(n): s = str(n); return s == s[::-1]
%o A347401 def aupton(terms):
%o A347401     alst, seen = [1], {1}
%o A347401     for n in range(2, terms+1):
%o A347401         an = 1
%o A347401         while an in seen or not ispal(n + an): an += 1
%o A347401         alst.append(an); seen.add(an)
%o A347401     return alst
%o A347401 print(aupton(200)) # _Michael S. Branicky_, Aug 30 2021
%Y A347401 Cf. A347335, A347336, A347400, A347402.
%K A347401 base,nonn
%O A347401 1,2
%A A347401 _Eric Angelini_ and _Carole Dubois_, Aug 30 2021