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Search: id:A092063
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| A092063 |
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Numbers n such that numerator of Sum_{i=1..n} 1/(prime(i)-1) is prime. |
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+0
7
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| 2, 3, 4, 7, 8, 15, 19, 21, 22, 25, 26, 31, 34, 45, 46, 52, 65, 69, 79, 85, 89, 98, 102, 122, 137, 149, 181, 195, 210, 220, 316, 325, 340, 385, 436, 466, 497, 934, 972, 1180, 1211, 1212, 1639, 1807, 1807, 2075, 2104, 3100
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Note that the definition here is subtly different from that of A092065.
Terms a(k) < 1000 correspond to primes. Beyond, numerators are strong pseudoprimes. Note that A120271(3100) has 2187 digits. - M. F. Hasler (Maximilian.Hasler(AT)gmail.com), Feb 06 2008
Intersection of A000040 (the primes) and A120271 (numerators of partial sums of 1/(prime(i)-1)). - M. F. Hasler (Maximilian.Hasler(AT)gmail.com), Feb 06 2008
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EXAMPLE
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1/(2-1) + 1/(3-1) = 3/2 and 3 is prime so a(1)=2
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PROGRAM
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(PARI) f(n)= s=0; for(i=1, n, s=s+1/(prime(i)-1)); return(s); for (i=1, 500, if(isprime(numerator(f(i))), print1(i, ", ")));
(PARI) print_A092063( i=0 /* start testing at i+1 */)={local(s=sum(j=1, i, 1/(prime(j)-1))); while(1, while(!ispseudoprime(numerator(s+=1/(prime(i++)-1))), ); print1(i", "))} - M. F. Hasler (Maximilian.Hasler(AT)gmail.com), Feb 06 2008
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CROSSREFS
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Cf. A092064, A120271.
Sequence in context: A097110 A116961 A120611 this_sequence A126850 A007497 A126882
Adjacent sequences: A092060 A092061 A092062 this_sequence A092064 A092065 A092066
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KEYWORD
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hard,nonn
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AUTHOR
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Mohammed Bouayoun (mohammed.bouayoun(AT)sanef.com), Feb 20 2004
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EXTENSIONS
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More terms from M. F. Hasler (Maximilian.Hasler(AT)gmail.com), Feb 06 2008
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