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 A266139 Volcano palindromes: palindromes not in A110784 such that removing one digit will result in a term in A110784. 2
 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 101, 202, 212, 303, 313, 323, 404, 414, 424, 434, 505, 515, 525, 535, 545, 606, 616, 626, 636, 646, 656, 707, 717, 727, 737, 747, 757, 767, 808, 818, 828, 838, 848, 858, 868, 878, 909, 919, 929, 939, 949, 959, 969, 979, 989, 11011 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS All terms have odd number of digits. Terms are palindromes such that digits are nondecreasing halfway through except for the middle digit, which is strictly smaller than its neighboring digits. Illustration using a term of this sequence, 23446564432: .  .  .  .  6  .  6  .  .  .  . .  .  .  .  .  5  .  .  .  .  . .  .  4  4  .  .  .  4  4  .  . .  3  .  .  .  .  .  .  .  3  . 2  .  .  .  .  .  .  .  .  .  2 LINKS Chai Wah Wu, Table of n, a(n) for n = 1..10000 PROG (Python) from itertools import combinations_with_replacement as mc def agentod(digits):     yield from range(10)     for d in range(3, digits+1, 2):         for left in mc("123456789", d//2):             for center in range(int(left[-1])):                 yield int("".join(left + (str(center), ) + left[::-1])) print([an for an in agentod(5)]) # Michael S. Branicky, Aug 21 2021 CROSSREFS Cf. A110784. Sequence in context: A030147 A207954 A193412 * A154562 A193409 A280823 Adjacent sequences:  A266136 A266137 A266138 * A266140 A266141 A266142 KEYWORD nonn,easy,base AUTHOR Chai Wah Wu, Dec 25 2015 STATUS approved

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Last modified December 4 22:42 EST 2021. Contains 349526 sequences. (Running on oeis4.)