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 A068061 Palindromic numbers j that are not of the form k + reverse(k) for any k. 2
 1, 3, 5, 7, 9, 111, 131, 151, 171, 191, 212, 232, 252, 272, 292, 313, 333, 353, 373, 393, 414, 434, 454, 474, 494, 515, 535, 555, 575, 595, 616, 636, 656, 676, 696, 717, 737, 757, 777, 797, 818, 838, 858, 878, 898, 919, 939, 959, 979, 999, 10101, 10301, 10501 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Intersection of A002113 and A067031. Every palindrome with an even number of digits is of the form k + reverse(k), for example 123321 = 123000 + 000321, so the sequence has no terms with an even number of digits. It seems that the terms follow a strict pattern: x1x', x3x', x5x', x7x', x9x', y1y', y3y', y5y', y7y', y9y' and so on. x' is reverse(x). Apart from the first 5 terms in the sequence, the surrounding terms (x and y) simply iterate over the positive integers. - Dmitry Kamenetsky, Mar 10 2017 Every palindrome with an odd number of digits is of the form k + reverse(k) if the central digit is even, for example 1234321 = 1232000 + 0002321, so no term with an odd number of digits has an even central digit. - A.H.M. Smeets, Feb 01 2019 LINKS Michel Marcus, Table of n, a(n) for n = 1..500 EXAMPLE 9 belongs to this sequence, since there is no k such that k + reverse(k) = 9 (cf. A067031). PROG (PARI) isok(n) = {if (Pol(d=digits(n)) == Polrev(d), for (k=1, n-1, if (k + fromdigits(Vecrev(digits(k))) == n, return (0)); ); 1; ); } \\ Michel Marcus, Mar 12 2017 CROSSREFS Cf. A002113, A067031, A068062. Sequence in context: A070788 A030148 A364836 * A332970 A316492 A062887 Adjacent sequences: A068058 A068059 A068060 * A068062 A068063 A068064 KEYWORD base,easy,nonn AUTHOR Klaus Brockhaus, Feb 15 2002 STATUS approved

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Last modified December 10 04:38 EST 2023. Contains 367699 sequences. (Running on oeis4.)