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Search: id:A083754
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| A083754 |
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a(1) = 1 and then smallest odd number not occurring earlier such that the concatenation a(1)a(2)a(3)... is a prime. |
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+0
2
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| 1, 3, 7, 11, 9, 27, 63, 31, 53, 21, 13, 83, 33, 39, 49, 51, 77, 87, 307, 29, 229, 281, 151, 173, 481, 41, 99, 157, 177, 17, 357, 213, 231, 171, 271, 557, 67, 113, 463, 159, 119, 57, 247, 147, 563, 409, 353, 391, 179, 1051, 209, 19, 153, 621, 287, 567, 313, 117, 363
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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Conjecture: all odd numbers not of the type 10k+5 are members.
Some of the larger entries may only correspond to probable primes.
Values corresponding to a(6)=27 (A083755(5)) through a(59)=363 (A083755(58), a 149-digit value) have been certified prime with Primo. - Rick L. Shepherd (rshepherd2(AT)hotmail.com), May 10 2003
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EXAMPLE
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13,137,13711, etc. are primes.(1379 is not a prime) hence 11 is the next member after 7.
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PROGRAM
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(PARI) {used_before(v, n) = for (l=1, matsize(v)[2], if(v[l]==n, return(1))); return(0)} {A083754=[1]; p=A083754[1]; A083755=[]; print1(A083754[1], ", "); for (m=2, 151, k=1; while (used_before(A083754, k)||!isprime(tmp_p=p*(10^length(Str(k)))+k), k=k+2); p=tmp_p; A083755=concat(A083755, p); A083754=concat(A083754, k); print1(A083754[m], ", ")); A083755}
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CROSSREFS
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Cf. A083755.
Sequence in context: A093931 A153788 A167486 this_sequence A043345 A023718 A076184
Adjacent sequences: A083751 A083752 A083753 this_sequence A083755 A083756 A083757
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KEYWORD
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base,nonn
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AUTHOR
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Amarnath Murthy and Meenakshi Srikanth (amarnath_murthy(AT)yahoo.com), May 06 2003
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EXTENSIONS
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More terms from Rick L. Shepherd (rshepherd2(AT)hotmail.com), May 08 2003
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