OFFSET
1,2
COMMENTS
This sequence is not a permutation of the integers > 0 as integers with digitsum 11, or 22, or 33, for instance, will not show.
LINKS
Jean-Marc Falcoz, Table of n, a(n) for n = 1..10001
EXAMPLE
The sequence starts with 1,2,3,4,5,6,10,7,11,9,... and we see indeed that the digits of:
{a(1); a(2)} have sum 1 + 2 = 3 (palindrome);
{a(2); a(3)} have sum 2 + 3 = 5 (palindrome);
{a(3); a(4)} have sum 3 + 4 = 7 (palindrome);
{a(4); a(5)} have sum 4 + 5 = 9 (palindrome);
{a(5); a(6)} have sum 5 + 6 = 11 (palindrome);
{a(6); a(7)} have sum 6 + 1 + 0 = 7 (palindrome);
{a(7); a(8)} have sum 1 + 0 + 7 = 8 (palindrome);
{a(8); a(9)} have sum 7 + 1 + 1 = 9 (palindrome);
{a(9); a(10)} have sum 1 + 1 + 9 = 11 (palindrome);
etc.
MATHEMATICA
a[1]=1; a[n_]:=a[n]=(k=1; While[MemberQ[Array[a, n-1], k]|| !PalindromeQ@Total[Join[IntegerDigits@a[n-1], IntegerDigits@k]], k++]; k)
Array[a, 68] (* Giorgos Kalogeropoulos, Jul 14 2023 *)
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Eric Angelini and Jean-Marc Falcoz, Jun 19 2019
STATUS
approved