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A307850
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Number of palindromic triangular numbers of length n whose index is also palindromic.
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0
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4, 1, 0, 1, 1, 1, 1, 0, 0, 1, 1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
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OFFSET
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1,1
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LINKS
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EXAMPLE
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There is only one palindromic triangular number of length 2 whose index is also palindromic. 11->66. Thus, a(2)=1.
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MATHEMATICA
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A003098 = Select[PolygonalNumber[3, Range[0, 10^6]], PalindromeQ]
(* Set Range to level of desired running time. *)
A008509 = Select[Range[0, 10^6], PalindromeQ[PolygonalNumber[3, #]] &]
(* Set Range to level of desired running time. *)
Table[Length[ Select[A008509[[Table[ Select[Range[35], IntegerLength[A003098[[#]]] == n || (n == 1 && A003098[[#]] == 0) &], {35}][[n]]]], PalindromeQ[#] &]], {n, 11}]
(* Set the first two Ranges to encompass the length of A003098 and the last Range to encompass the length of the last value in A003098. *)
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CROSSREFS
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KEYWORD
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nonn,base,hard
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AUTHOR
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STATUS
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approved
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