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Search: id:A088269
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| A088269 |
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Palindromic primes that yield a prime when sandwiched between two 1's. (Prefixing and suffixing a one on both sides yields another pal prime). |
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+0
5
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| 3, 5, 131, 383, 797, 11411, 16061, 16361, 19391, 33533, 36263, 73037, 75557, 79397, 1074701, 1126211, 1145411, 1175711, 1221221, 1243421, 1287821, 1303031, 1311131, 1328231, 1363631, 1489841, 1579751, 1600061, 1707071, 1748471
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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There are two 1-digit such n's, three 3-digit n's, nine 5-digit n's, 93 7-digit n's, 241 9-digit n's and no n with even number of digits. - Zak Seidov (zakseidov(AT)yahoo.com), Feb 23 2005
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EXAMPLE
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Start with 11;
insert a(2)=5 between digits of 11, 151 is prime;
insert a(3)=131 between digits of 11, 11311 is prime,
insert a(10)=33533 between digits of 11, 1335331 is prime, etc.
797 is a member as 17971 is also a prime.
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MATHEMATICA
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Do[If[PrimeQ[n] && Reverse[IntegerDigits[n]] == IntegerDigits[n] && PrimeQ[ToExpression["1" <> ToString[n*10+1]]], Print[n]], {n, 1, 2*10^6}] (Propper)
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CROSSREFS
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Cf. A088270, A088271, A088272.
Adjacent sequences: A088266 A088267 A088268 this_sequence A088270 A088271 A088272
Sequence in context: A105526 A070743 A103993 this_sequence A164371 A108013 A087307
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KEYWORD
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base,nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Sep 28 2003
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EXTENSIONS
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More terms from Ryan Propper (rpropper(AT)stanford.edu), Jul 09 2005
Entry revised by N. J. A. Sloane (njas(AT)research.att.com), Apr 29 2007
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