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Search: id:A077775
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| A077775 |
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Palindromic wing primes (a.k.a. near-repdigit palindromes) of the form (10^a(n)-1)/3-2*10^[ a(n)/2 ]. |
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31
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| 3, 7, 15, 123, 181, 185, 539, 597, 643, 743, 1553, 3135, 4769, 5133, 6177, 11733, 16103, 18997, 25271, 49025
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Prime versus probable prime status and proofs are given in the author's table.
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REFERENCES
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C. Caldwell and H. Dubner, "Journal of Recreational Mathematics", Volume 28, No. 1, 1996-97, pp. 1-9.
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LINKS
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Patrick De Geest, World!Of Numbers, Palindromic Wing Primes (PWP's)
Makoto Kamada, Factorizations of 33...33133...33
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EXAMPLE
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a(n)=15 -> (10^15-1)/3-2*10^7 = 333333313333333.
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MATHEMATICA
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Do[ If[ PrimeQ[(10^n - 6*10^Floor[n/2] - 1)/3], Print[n]], {n, 3, 49100, 2}] (from Robert G. Wilson v (rgwv(at)rgwv.com), Dec 16 2005)
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CROSSREFS
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Cf. A004023, A077775-A077798, A107123-A107127, A107648, A107649, A114633-A114647.
Adjacent sequences: A077772 A077773 A077774 this_sequence A077776 A077777 A077778
Sequence in context: A023370 A096422 A154795 this_sequence A033089 A153578 A018852
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KEYWORD
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nonn,base
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AUTHOR
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Patrick De Geest (pdg(AT)worldofnumbers.com), Nov 16 2002.
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