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%I #13 Mar 07 2024 08:50:50
%S 49,121,1207,22801,36481,117907,863041,11986939,32021347,83148061,
%T 88245211,106110601,217297081,238733401,242587711,461772733,487538353,
%U 606191323,683819293,700500007,758794243,966634069,989479087,995821039,1117186159,1205213749,1208515279
%N Products of two reversible primes that are the reverse of each other such that the products are also the sum of three consecutive primes.
%H Chai Wah Wu, <a href="/A130007/b130007.txt">Table of n, a(n) for n = 1..10000</a>
%e 121 = 11 * 11 = 37 + 41 +43
%e 1207 = 17 * 71 = 397 + 401 + 409
%e 117907 = 157 * 751 = 39293 + 39301 + 39313
%t PrevPrim[n_] := Block[{k = n - 1}, While[ !PrimeQ[k], k-- ]; k]; NextPrim[n_] := Block[{k = n + 1}, While[ !PrimeQ[k], k++ ]; k]; pal[n_] := FromDigits@ Reverse@ IntegerDigits@n; fQ[n_] := Block[{pn = pal@n, p, q, r, s}, q = PrevPrim[ Ceiling[n*pn/3]]; p = PrevPrim@q; r = NextPrim[ Floor[n*pn/3]]; s = NextPrim@r; n*pn == p + q + r || n*pn == q + r + s]; pd = 6; lst = {}; Do[ pd = NextPrim@pd; If[ PrimeQ@pd && fQ@pd, Print[pd*pal@pd]; AppendTo[lst, pd*pal@pd]], {n, 1000}]; lst = Union@lst (* _Robert G. Wilson v_, Jun 19 2007 *)
%Y Cf. A007500.
%K base,nonn
%O 1,1
%A _Paolo P. Lava_ and _Giorgio Balzarotti_, Jun 15 2007
%E Corrected and extended by _Robert G. Wilson v_, Jun 19 2007
%E Corrected and extended and definition clarified by _Chai Wah Wu_, Feb 25 2018
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