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

8, 9, 14, 16, 32

Offset

1,1

Links

Table of n, a(n) for n=1..5.

P. De Geest, Palindromic heptagonals

Mathematica

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};
A059869[n_] := Length[Select[A054910, IntegerLength[#] == n || (n == 1 && # == 0) &]];
Select[Range[19], A059869[#] == 0 &] (* Robert Price, Apr 28 2019 *)

Crossrefs

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

Sequence in context: A174041 A096784 A175859 * A327863 A213016 A373478

Adjacent sequences: A059866 A059867 A059868 * A059870 A059871 A059872

Keyword

nonn,base,hard

Author

Patrick De Geest, Feb 15 2000

Status

approved