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A371899
The (2n-1)st pair of terms and the (2n)th pair of terms share the same palindromic digit succession. This is the lexicographically earliest sequence of distinct terms > 0 with this property.
1
1, 221, 12, 21, 2, 332, 23, 32, 3, 113, 31, 13, 4, 114, 41, 14, 5, 115, 51, 15, 6, 116, 61, 16, 7, 117, 71, 17, 8, 118, 81, 18, 9, 119, 91, 19, 10, 2201, 102, 201, 11, 2211, 112, 211, 20, 3302, 203, 302, 22, 3322, 223, 322, 24, 142, 241, 42, 25, 152, 251, 52, 26, 162, 261, 62, 27, 172, 271, 72, 28, 182, 281, 82, 29, 192, 291, 92, 30
OFFSET
1,2
LINKS
Giorgos Kalogeropoulos, Table of n, a(n) for n = 1 to 9999
Eric Angelini, Palindromaniac, Personal blog, April 2024.
EXAMPLE
The 1st pair of terms (1,221) and the 2nd one (12,21) share the same palindromic digit succession.
The 3rd pair of terms (2,332) and the 4th one (23,32) share the same palindromic digit succession.
The 5th pair of terms (3,113) and the 6th one (31,13) share the same palindromic digit succession. Etc.
MATHEMATICA
lst={1}; Do[While[f=Flatten[IntegerDigits/@{Last@lst, k}];
f1=First@SortBy[Select[Table[FromDigits/@TakeDrop[f, m], {m, Length@f-1}], ContainsNone[lst, #]&], First];
!ListQ@f1||MemberQ[lst, k]||ContainsAny[lst, f1]||Equal@@f1||!PalindromeQ@f, k++];
lst=Join[lst, {k}, f1]; k=1; While[MemberQ[lst, k], k++]; AppendTo[lst, k], {w, 20}]; lst
CROSSREFS
Cf. A371113.
Sequence in context: A167825 A339680 A266237 * A159565 A330281 A345512
KEYWORD
base,nonn,look
AUTHOR
STATUS
approved