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Search: id:A130007
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| A130007 |
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Products of two palindromic primes that are also the sum of three consecutive primes. |
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+0
1
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| 49, 121, 1207, 22801, 36481, 75463, 117907, 215821, 863041, 2726521, 4787653, 5475883, 6292153, 6635593, 6931075, 7479643, 10273537, 10881199, 11986939, 12722419, 14203129, 15502339, 15653239, 15926995, 16700239, 18665209
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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121 = 11 * 11 = 37 + 41 +43
1207 = 17 * 71 = 397 + 401 + 409
117907 = 157 * 751 = 39293 + 39301 + 39313
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MATHEMATICA
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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 (rgwv(AT)rgwv.com), Jun 19 2007
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CROSSREFS
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Cf. A007500.
Sequence in context: A115557 A167718 A080665 this_sequence A044300 A044681 A020256
Adjacent sequences: A130004 A130005 A130006 this_sequence A130008 A130009 A130010
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KEYWORD
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base,nonn
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AUTHOR
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Paolo P. Lava & Giorgio Balzarotti (ppl(AT)spl.at), Jun 15 2007
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EXTENSIONS
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Corrected and extended by Robert G. Wilson v (rgwv(AT)rgwv.com), Jun 19 2007
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