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%I #26 Jun 03 2026 15:27:22
%S 2,5,9,12,18,20,30,34,41,42,48,49
%N Numbers k such that there are no oblong (promic) palindromes of length k.
%D Elena Deza and Michel Marie Deza, Figurate numbers, World Scientific Publishing (2012), page 278.
%H Patrick De Geest, <a href="https://www.worldofnumbers.com/consec.htm">Palindromic pronic numbers of the form n(n+1)</a>.
%Y Cf. A002378, A028336, A028337.
%K nonn,base,hard,more
%O 1,1
%A _Patrick De Geest_, Oct 15 1998
%E a(9)-a(12) from Patrick De Geest's website added by _Max Alekseyev_, Jun 03 2026