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Search: id:A160218
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| A160218 |
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Index at which n-th prime occurs in A160256, or -1 if the prime never occurs. |
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+0
3
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OFFSET
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1,1
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COMMENT
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A160256(a(n))=A000040(n) if and only if both Conjectures 1 and 2 are true:
Conjecture 1: Primes occur in A160256 in increasing order.
Conjecture 2: All primes occur in A160256.
Conjecture 3: Except for A160256(4)=4, the least positive integer which does not occur in A160256 up to a given index is always a prime (and thus of the form A160256(a(k)) for some k).
Conjecture 4: A160256(a(n)) is always the least positive integer which did not occur earlier in A160256.
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PROGRAM
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(PARI) list_A160218(n)={ my(a1=1, a2=1, S=[]); until( isprime(a1) & !print1(#S, ", ") & !n--, for( a=1, 9e9, a*a1%a2 & next; setsearch(S, a) & next; a2=a1; S=setunion(S, Set(a1=a)); /*print1(a", "); */ next(2)); error); vecsort(eval(S)) }
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CROSSREFS
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Cf. A160256, A151413.
Sequence in context: A041010 A041733 A107083 this_sequence A081615 A157903 A024478
Adjacent sequences: A160215 A160216 A160217 this_sequence A160219 A160220 A160221
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KEYWORD
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hard,more,nonn
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AUTHOR
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M. F. Hasler (MHasler(AT)univ-ag.fr), May 06 2009
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EXTENSIONS
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Edited by N. J. A. Sloane, May 16 2009
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