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Search: id:A077202
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| A077202 |
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a(1) = 1, a(n) = smallest number such that the concatenation of two successive terms gives a prime which has not occurred earlier. |
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+0
2
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| 1, 1, 3, 1, 7, 1, 9, 7, 3, 7, 9, 11, 3, 11, 17, 3, 13, 1, 27, 1, 37, 3, 17, 9, 19, 1, 39, 7, 19, 3, 31, 19, 7, 27, 7, 33, 7, 39, 11, 23, 3, 47, 9, 29, 3, 49, 1, 49, 9, 37, 9, 41, 9, 47, 21, 1, 51, 13, 19, 9, 53, 23, 9, 67, 3, 53, 33, 13, 21, 11, 29, 17, 21, 13, 27, 11, 51, 19, 13, 61
(list; graph; listen)
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OFFSET
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0,3
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COMMENT
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Conjecture: Every odd prime occurs in this sequence infinitely many times.
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PROGRAM
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(PARI) A077202(nmax)= { local(a, tst, hadp, hSet) ; a=[1] ; hadp=[1] ; for(n=2, nmax, for(new=1, 10000, tst=Str(eval(a[n-1]) eval(new)) ; tst=eval(tst) ; if(isprime(tst), hSet=Set(hadp) ; if( setsearch(hSet, tst)==0, hadp=concat(hadp, tst) ; a=concat(a, new) ; break ; ) ; ) ; ) ; ) ; return(a) ; } { print(A077202(80)) ; } - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), May 19 2006
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CROSSREFS
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Sequence in context: A140435 A063754 A099749 this_sequence A086665 A050521 A098093
Adjacent sequences: A077199 A077200 A077201 this_sequence A077203 A077204 A077205
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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), Nov 02 2002
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EXTENSIONS
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Corrected and extended by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), May 19 2006
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