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A130007
Products of two reversible primes that are the reverse of each other such that the products are also the sum of three consecutive primes.
1
49, 121, 1207, 22801, 36481, 117907, 863041, 11986939, 32021347, 83148061, 88245211, 106110601, 217297081, 238733401, 242587711, 461772733, 487538353, 606191323, 683819293, 700500007, 758794243, 966634069, 989479087, 995821039, 1117186159, 1205213749, 1208515279
OFFSET
1,1
EXAMPLE
121 = 11 * 11 = 37 + 41 +43
1207 = 17 * 71 = 397 + 401 + 409
117907 = 157 * 751 = 39293 + 39301 + 39313
MATHEMATICA
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 *)
CROSSREFS
Cf. A007500.
Sequence in context: A115557 A167718 A080665 * A202331 A044300 A044681
KEYWORD
base,nonn
AUTHOR
EXTENSIONS
Corrected and extended by Robert G. Wilson v, Jun 19 2007
Corrected and extended and definition clarified by Chai Wah Wu, Feb 25 2018
STATUS
approved