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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 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
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

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Last modified March 28 18:04 EDT 2024. Contains 371254 sequences. (Running on oeis4.)