This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A116993 #15 Aug 22 2025 00:25:36
%S A116993 13,1,4,44,66,484,4444,7326,6666,48884,73326,493284,888888,666666,
%T A116993 5426124,4888884,6672666,7333326,44888844,73399326,246888642,67333266,
%U A116993 4073662593,4893772884,4533773244,6800659866,2715775062,1481331852,493777284,740665926,8147325186,5431550124,74807258526
%N A116993 a(n) is the least number having exactly n representations as a product of two palindromes.
%C A116993 a(20) <= 733333326; a(34) <= 666666666666; a(39) <= 4888888888884 and a(44) <= 7333333333326. - _Farideh Firoozbakht_, Dec 10 2006
%H A116993 David A. Corneth, <a href="/A116993/a116993.gp.txt">Some upper bounds on a(n)</a>
%e A116993 a(0)=13 since 13 is the smallest number that cannot be represented as a product of two palindromes.
%e A116993 a(5)=484 since 484 = 1*484 = 2*242 = 4*121 = 22*22 = 11*44.
%t A116993 f[n_]:=f[n]=Length[Select[Divisors[n], #<=n^(1/2)&&FromDigits[ Reverse[IntegerDigits[ # ]]]==#&&FromDigits[Reverse[IntegerDigits [n/# ]]]==n/#&]]; a[n_]:=(For[m=1, f[m] != n, m++ ]; m); Do[Print[a[n]], {n, 0, 18}] (* _Farideh Firoozbakht_, Dec 10 2006 *)
%Y A116993 Cf. A002113, A125832, A125833, A125834, A140332.
%K A116993 nonn,base
%O A116993 0,1
%A A116993 _Giovanni Resta_, Apr 02 2006
%E A116993 More terms from _Farideh Firoozbakht_, Dec 10 2006
%E A116993 a(19)-a(27) from _Donovan Johnson_, Aug 04 2009
%E A116993 More terms from _David A. Corneth_, Aug 10 2025