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 A069748 Numbers k such that k and k^3 are both palindromes. 7
 0, 1, 2, 7, 11, 101, 111, 1001, 10001, 10101, 11011, 100001, 101101, 110011, 1000001, 1001001, 1100011, 10000001, 10011001, 10100101, 11000011, 100000001, 100010001, 100101001, 101000101, 110000011, 1000000001, 1000110001, 1010000101, 1100000011, 10000000001 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS For an arithmetical function f, call the pairs (x,y) such that y = f(x) and x, y are palindromes the "palinpairs" of f. {a(n)} is then the sequence of abscissae of palinpairs of f(n) = n^3. Perhaps this sequence is the same as A002780, except for 2201. - Dmitry Kamenetsky, Apr 16 2009 For n >= 5, there are no terms with digit sum 5. Conjecture: all terms belong to one of 3 disjoint classes of the following forms: 10^k+1, 10^(2*t)+10^t+1, t > 0, and (10^u+1)*(10^v+1), u,v > 0, with digit sums 2, 3 and 4 correspondingly. - Vladimir Shevelev, May 31 2011 LINKS Michael S. Branicky, Table of n, a(n) for n = 1..117 Vladimir Shevelev, Re: numbers whose cube is a palindrome, seqfan list, May 25 2011 MATHEMATICA isPalin[n_] := (n == FromDigits[Reverse[IntegerDigits[n]]]); Do[m = n^3; If[isPalin[n] && isPalin[m], Print[{n, m}]], {n, 1, 10^6}] PROG (PARI) ispal(n) = my(d=digits(n)); d == Vecrev(d); isok(n) = ispal(n) && ispal(n^3); \\ Michel Marcus, Dec 16 2018 CROSSREFS Intersection of A002113 and A002780. Sequence in context: A085315 A002780 A069885 * A064441 A110949 A226703 Adjacent sequences: A069745 A069746 A069747 * A069749 A069750 A069751 KEYWORD base,nonn AUTHOR Joseph L. Pe, Apr 22 2002 EXTENSIONS a(29) and beyond from Michael S. Branicky, Aug 06 2022 STATUS approved

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Last modified October 2 15:29 EDT 2023. Contains 365837 sequences. (Running on oeis4.)