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Search: id:A089628
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| A089628 |
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Smallest member of a pair of consecutive twin prime pairs that have no primes between them. |
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+0
1
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| 3, 5, 11, 101, 137, 179, 191, 419, 809, 821, 1019, 1049, 1481, 1871, 1931, 2081, 2111, 2969, 3251, 3359, 3371, 3461, 4217, 4229, 4259, 5009, 5651, 5867, 6689, 6761, 6779, 6947, 7331, 7547, 8219, 8969, 9419, 9431, 9437, 10007, 11057, 11159, 11699, 12239
(list; graph; listen)
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OFFSET
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3,1
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COMMENT
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Run the pari script savetwins(100000) or so to build the twinprime array of lower bounds before you run the main script.
Except for first term, same as A053778. - David Wasserman (wasserma(AT)spawar.navy.mil), Feb 22 2006
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EXAMPLE
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Twin prime pairs 5,7 and 11,13 contain only the composite numbers 6,7,8,9,10
between them. So 5 is in the table. 11,13 and 17,19 have no primes between.
11 is in the table. 41,43 and 59,61 have primes 47 and 53 between then so 41
is not listed.
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PROGRAM
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(PARI) \save as twinpr.gp pbetweentw(n) = { forstep(x1=1, n, 2, c=0; t1 = twin[x1]; t2 = twin[x1+2]; for(y=t1+3, t2-1, if(isprime(y), c++) ); if(c==0, print1(t1", ")) ) } savetwins(n) = build a table of twin prime lower bounds { twin = vector(n); c=1; forprime(x=3, n, if(isprime(x+2), twin[c]=x; c++; ) ) }
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CROSSREFS
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Sequence in context: A046928 A089070 A068157 this_sequence A083841 A062601 A038198
Adjacent sequences: A089625 A089626 A089627 this_sequence A089629 A089630 A089631
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KEYWORD
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easy,nonn
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AUTHOR
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Cino Hilliard (hillcino368(AT)gmail.com), Jan 01 2004
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