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Index of the smallest n-digit palindromic triangular number, or 0 if no such number exists.
3

%I #9 Aug 11 2024 14:41:34

%S 1,10,18,77,173,1111,1593,8382,18906,50281,167053,0,1620621,6307938,

%T 15126258,50008881,149142458,846122222,2480116437,5513600773,

%U 14667896198,49786655918,246644446642,529670494286,2466444446642

%N Index of the smallest n-digit palindromic triangular number, or 0 if no such number exists.

%H P. De Geest, <a href="https://www.worldofnumbers.com/em_alltria.htm">Exhaustive list of Palindromic Triangulars</a>

%e a(4) = 77 as 77*78/2 = 3003 is the smallest 4-digit palindromic triangular number.

%e a(12) = 0 as no 12-digit palindromic triangular number exists.

%Y Cf. A068641, A068643, A068644, A000217, A003098, A008509, A008510, A054263.

%K base,nonn

%O 1,2

%A _Amarnath Murthy_, Feb 28 2002

%E Edited by _Patrick De Geest_, Mar 24 2002