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 A193409 Crater numbers. 2
 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 101, 212, 323, 434, 545, 656, 767, 878, 989, 21012, 32123, 43234, 54345, 65456, 76567, 87678, 98789, 3210123, 4321234, 5432345, 6543456, 7654567, 8765678, 9876789, 432101234, 543212345, 654323456, 765434567, 876545678, 987656789, 54321012345, 65432123456, 76543234567, 87654345678, 98765456789, 6543210123456, 7654321234567, 8765432345678, 9876543456789, 765432101234567, 876543212345678, 987654323456789, 87654321012345678, 98765432123456789, 9876543210123456789 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS For n>9 the structure of digits represents a crater. The first and last digit of each term are identical. The first digits are in consecutive decreasing order. The last digits are in consecutive increasing order. The numbers have only one smallest digit. The number of digits is odd. This sequence is finite with 55 terms. The final term is 9876543210123456789. Finite subset of primes of this sequence: 2, 3, 5, 7, 101, 7654567. There are 11 - k terms with 2*k - 1 digits. - Omar E. Pol, Aug 04 2011 LINKS Table of n, a(n) for n=1..55. EXAMPLE Illustration using a(32)=7654567: 7 . . . . . 7 . 6 . . . 6 . . . 5 . 5 . . . . . 4 . . . MATHEMATICA Flatten[Table[FromDigits/@(Join[Reverse[Rest[#]], #]&/@Partition[ Range[ 0, 9], n, 1]), {n, 10}]] (* Harvey P. Dale, Dec 27 2018 *) PROG (Python) ups = [tuple(range(i, j)) for i in range(10) for j in range(i+1, 11)] afull = sorted(int("".join(map(str, u[::-1] + u[1:]))) for u in ups) print(afull) # Michael S. Branicky, Aug 02 2022 CROSSREFS Subset of palindromes (A002113), A193412 and valley numbers (A193413). Cf. A134810, A134970. - Omar E. Pol, Aug 04 2011 Sequence in context: A193412 A266139 A154562 * A280823 A367342 A302656 Adjacent sequences: A193406 A193407 A193408 * A193410 A193411 A193412 KEYWORD base,fini,full,nonn AUTHOR Jaroslav Krizek, Jul 25 2011 EXTENSIONS Corrected and extended by Jaroslav Krizek, Jul 27 2011 STATUS approved

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Last modified August 6 13:04 EDT 2024. Contains 374974 sequences. (Running on oeis4.)