cp's OEIS Frontend

A134810 Giza numbers.

%I A134810 #29 Apr 12 2025 09:51:24
%S A134810 1,2,3,4,5,6,7,8,9,121,232,343,454,565,676,787,898,12321,23432,34543,
%T A134810 45654,56765,67876,78987,1234321,2345432,3456543,4567654,5678765,
%U A134810 6789876,123454321,234565432,345676543,456787654,567898765,12345654321,23456765432
%N A134810 Giza numbers.
%C A134810 For n > 9 the structure of digits represents the pyramids of Giza. Also the top of a mountain. The first digit is equal to the last digit. The first digits are in consecutive increasing order. The last digits are in consecutive decreasing order. The largest digit is the central digit. The number of digits is odd. This sequence has 45 terms. The final term is 12345678987654321. Giza numbers are mountain numbers A134941 and palindromes A002113.
%C A134810 There are 10 - k numbers with 2*k - 1 digits. - _Omar E. Pol_, Aug 04 2011
%H A134810 Nathaniel Johnston, <a href="/A134810/b134810.txt">Table of n, a(n) for n = 1..45</a> (full sequence)
%F A134810 A178333(a(n))*A136522(a(n)) = 1. - _Reinhard Zumkeller_, May 25 2010
%e A134810 Illustration using the final term of this sequence:
%e A134810   . . . . . . . . 9 . . . . . . . .
%e A134810   . . . . . . . 8 . 8 . . . . . . .
%e A134810   . . . . . . 7 . . . 7 . . . . . .
%e A134810   . . . . . 6 . . . . . 6 . . . . .
%e A134810   . . . . 5 . . . . . . . 5 . . . .
%e A134810   . . . 4 . . . . . . . . . 4 . . .
%e A134810   . . 3 . . . . . . . . . . . 3 . .
%e A134810   . 2 . . . . . . . . . . . . . 2 .
%e A134810   1 . . . . . . . . . . . . . . . 1
%t A134810 ups = Flatten[Table[Range[i, j - 1], {i, 1, 9}, {j, i + 1, 10}], 1];afull = Sort[  Map[ToExpression@StringJoin@Map[ToString, #[[;; -2]] ~Join~ Reverse[#]] &, ups]];afull (* _James C. McMahon_, Apr 11 2025 *)
%o A134810 (Python)
%o A134810 ups = [tuple(range(i, j)) for i in range(1, 10) for j in range(i+1, 11)]
%o A134810 afull = sorted(int("".join(map(str, u[:-1] + u[::-1]))) for u in ups)
%o A134810 print(afull) # _Michael S. Branicky_, Aug 02 2022
%Y A134810 Cf. A002113, A134941.
%K A134810 easy,fini,full,nonn,base
%O A134810 1,2
%A A134810 _Omar E. Pol_, Nov 25 2007, Nov 26 2007