cp's OEIS Frontend

A294924 Numbers n such that the whole sequence of the first n terms of A293699 is a palindrome.

%I A294924 #16 Feb 26 2018 12:14:31
%S A294924 1,3,5,7,26,63,100,137,174,211,248,285,322,359,396,433,470,507,544,
%T A294924 581,618,655,692,729,766,803,840,877,914,951,988,1025,1062,1099,1136,
%U A294924 1173,1210,1247,1284,1321,1358,1395,1432,1469,1506,1543,1580,1617,1654,1691,1728,1765,1802,1839,1876,1913,1950,1987,2024,2061,2098,2135
%N A294924 Numbers n such that the whole sequence of the first n terms of A293699 is a palindrome.
%C A294924 A293699 are the first differences of A293751 which are the positive integers i such that floor(tan(-i))=1.
%C A294924 A293702 are the lengths of the longest palindromic subsequences in the first n terms of A293699.
%H A294924 V.J. Pohjola, <a href="https://palindromesdotblog.files.wordpress.com/2018/02/ny-1-7-a294924.pdf">Line plot for n=1..7</a>
%H A294924 V.J. Pohjola, <a href="https://palindromesdotblog.files.wordpress.com/2018/02/logny-1-85-a294924.pdf">Line plot for n=1..85</a>
%e A294924 The first 7 terms of A293699 are (3, 19, 3, 19, 3, 19, 3) which is a palindromic sequence, so 7 is a term.
%e A294924 The first 8 terms of A293699 are (3, 19, 3, 19, 3, 19, 3, 3) which is not a palindromic sequence, so 8 is not a term.
%e A294924 The first 9 terms of A293699 are (3, 19, 3, 19, 3, 19, 3, 3, 16) which is not a palindromic sequence, so 9 is not a term.
%e A294924 The first 25 terms of A293699 are (3, 19, 3, 19, 3, 19, 3, 3, 16, 3, 3, 16, 3, 3, 16, 3, 3, 16, 3, 3, 19, 3, 19, 3, 19) which is not a palindromic sequence, so 25 is not a term.
%e A294924 The first 26 terms of A293699 are (3, 19, 3, 19, 3, 19, 3, 3, 16, 3, 3, 16, 3, 3, 16, 3, 3, 16, 3, 3, 19, 3, 19, 3, 19, 3) which is a palindromic sequence, so 26 is a term.
%t A294924 rootsn7 = Flatten[Position[Table[Floor[Tan[-n]], {n, 1, 10^7}], 1]];
%t A294924 difn7 = Differences[rootsn7];
%t A294924 ny = {}; Do[
%t A294924 If[Table[difn7[[i]], {i, 1, n}] == Reverse[Table[difn7[[i]], {i, 1, n}]],
%t A294924   AppendTo[ny, n]], {n, 1, Length[difn7]}]
%t A294924 ny
%Y A294924 Cf. A293702, A293699, A293751, A294923.
%K A294924 nonn
%O A294924 1,2
%A A294924 _V.J. Pohjola_, Nov 11 2017