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A059869 Numbers k such that there exist no palindromic heptagonals of length k. 7

%I

%S 8,9,14,16,32

%N Numbers k such that there exist no palindromic heptagonals of length k.

%H P. De Geest, <a href="http://www.worldofnumbers.com/hepta.htm">Palindromic heptagonals</a>

%t A054910 = {0, 1, 7, 55, 616, 3553, 4774, 60606, 848848, 4615164, 5400045, 6050506, 7165445617, 62786368726, 65331413356, 73665056637, 91120102119, 345546645543, 365139931563, 947927729749, 3646334336463, 7111015101117, 717685292586717, 19480809790808491, 615857222222758516, 1465393008003935641, 8282802468642082828, 15599378333387399551, 20316023422432061302};

%t A059869[n_] := Length[Select[A054910, IntegerLength[#] == n || (n == 1 && # == 0) &]];

%t Select[Range[19], A059869[#] == 0 &] (* _Robert Price_, Apr 28 2019 *)

%Y Cf. A034822, A034307, A059868, A059870, A000566, A054971, A054910.

%K nonn,base,hard

%O 1,1

%A _Patrick De Geest_, Feb 15 2000

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Last modified October 23 21:57 EDT 2019. Contains 328373 sequences. (Running on oeis4.)