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 A008510 Numbers k such that both k and the k-th triangular number are palindromes. 11
 1, 2, 3, 11, 77, 363, 1111, 2662, 111111, 246642, 11111111, 363474363, 2664444662, 26644444662, 246644446642, 266444444662, 2466444446642, 3654345456545434563 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 REFERENCES D. Wells, The Penguin Dictionary of Curious and Interesting Numbers. Penguin Books, NY, 1986, 93. LINKS Table of n, a(n) for n=1..18. Patrick De Geest, Subsets of palindromic triangulars Patrick De Geest, For the last term MATHEMATICA palQ[n_] := Reverse[x = IntegerDigits[n]] == x; t = {}; Do[If[palQ[n] && palQ[n*(n + 1)/2], AppendTo[t, n]], {n, 1.2*10^7}]; t (* Jayanta Basu, May 15 2013 *) CROSSREFS Sequence in context: A338613 A109132 A279084 * A290512 A042165 A089921 Adjacent sequences: A008507 A008508 A008509 * A008511 A008512 A008513 KEYWORD nonn,base,more AUTHOR Patrick De Geest STATUS approved

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Last modified September 23 00:10 EDT 2023. Contains 365532 sequences. (Running on oeis4.)