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A125832 Numbers n which have exactly 14 representations as a product of two palindromes. 2

%I #4 Mar 30 2012 17:37:44

%S 5426124,8139186,20017998,21999978,26690664,26888862,29333304,

%T 49821684,73267326,97689768,98666568,146534652,147999852,220197978,

%U 271333062,274019262,320221902,403696293,471535064,489372884,516019504,518221704

%N Numbers n which have exactly 14 representations as a product of two palindromes.

%e 26888862 is in the sequence since 26888862 = 1*26888862 = 2*13444431

%e = 11*2444442 = 22*1222221 = 111*242242 = 121*222222 = 222*121121

%e = 242*111111 = 1001*26862 = 1221*22022 = 1331*20202 = 2002*13431

%e = 2442*11011 = 2662*10101.

%t f[n_]:=f[n]=Length[Select[Divisors[n],#<=n^(1/2)&&FromDigits[ Reverse[IntegerDigits[ # ]]]==#&&FromDigits[Reverse[IntegerDigits [n/# ]]]==n/#&]];Do[If[f[n]==14,Print[n]],{n,50000000}]

%Y Cf. A116993, A125833, A125834.

%K base,nonn

%O 1,1

%A _Farideh Firoozbakht_, Dec 10 2006

%E a(9)-a(22) from _Donovan Johnson_, Aug 05 2009

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Last modified June 17 18:04 EDT 2024. Contains 373463 sequences. (Running on oeis4.)