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Search: id:A133478
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| A133478 |
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a(n) = smallest semiprime s1 such that there is no prime between s1 and s2=nextsemiprime(s1)=s1+n. |
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+0
2
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| 9, 49, 62, 403, 341, 843, 6722, 3473, 2869, 14059, 18467, 26603, 166126, 41779, 74491, 192061, 463161, 226489, 344119, 517421, 943606, 2171131, 4577519, 584213, 2560177, 4356633, 8367139, 11174753, 13191293, 7319797, 27841051, 10644122, 13683034, 29492893, 47735342, 26837363, 63305661, 90455097, 189662206, 120175651
(list; graph; listen)
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OFFSET
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1,1
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LINKS
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Jacques Tramu (jacques.tramu(AT)echolalie.com), Dec 25 2007, Table of n, a(n) for n = 1..49
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EXAMPLE
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a(1)=9 because there is no prime between 9 and 10.
a(2)=49 because there is no prime between 49 and 51.
a(3)=62 because there is no prime between 62 and 65.
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MATHEMATICA
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sp = Import["~/b001358.txt", "Table"][[All, 2]]
Block[{n = 1, result = {}, tmp},
While[(tmp = Select[sp,
MemberQ[sp, #1 + n] &&
And @@ (FreeQ[sp, #1] & ) /@
Range[ #1 + 1, #1 + n - 1 ] && Select[ Range[ #1, #1 + n ], PrimeQ, 1 ] == {} &, 1 ]) != {},
result = Join[result, tmp]; n++ ];
result] (Peter Pein <petsie@dordos.net>), Dec 23 2007
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CROSSREFS
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Sequence in context: A007037 A072461 A012260 this_sequence A032589 A137175 A028375
Adjacent sequences: A133475 A133476 A133477 this_sequence A133479 A133480 A133481
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KEYWORD
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nonn
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AUTHOR
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Jack Brennen (jb(AT)brennen.net) and Zak Seidov (zakseidov(AT)yahoo.com), Dec 23 2007
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EXTENSIONS
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a(37)-a(40) from Jacques Tramu (jacques.tramu(AT)echolalie.com), Dec 23 2007
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