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%I #7 Mar 30 2012 17:40:41
%S 13,1,4,44,66,484,4444,7326,6666,48884,73326,493284,888888,666666,
%T 5426124,4888884,6672666,7333326,44888844,73399326,246888642,67333266,
%U 4073662593,4893772884,4533773244,6800659866,2715775062,1481331852
%N a(n) is the least number having exactly n representations as a product of two palindromes.
%C a(20) <= 733333326; a(34) <= 666666666666; a(39) <= 4888888888884 and a(44) <= 7333333333326. - _Farideh Firoozbakht_, Dec 10 2006
%e a(0)=13 since 13 is the smallest number that cannot be represented as a product of two palindromes. a(5)=484 since 484= 1*484 = 2*242 = 4*121 = 22*22 = 11*44.
%t 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 Cf. A002113, A125832, A125833, A125834.
%K base,nonn
%O 0,1
%A _Giovanni Resta_, Apr 02 2006
%E More terms from _Farideh Firoozbakht_, Dec 10 2006
%E a(19)-a(27) from _Donovan Johnson_, Aug 04 2009
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