Search: id:A118306
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%I A118306
%S A118306 1,3,2,9,7,15,5,27,4,21,13,45,11,33,6,81,19,75,17,63,10,39,29,135,49,51,
%T A118306 8,99,23,105,37,243,14,57,77,225,31,69,22,189,43,165,41,117,12,87,53,
%U A118306 405,25,147,26,153,47,375,91,297,34,93,61,315,59,111,20,729,119,195,71
%N A118306 If n = product(k>=1} p(k)^b(n,k), where p(k) is the k-th prime and where 
               each b(n,k) is a nonnegative integer, then: If n occurs earlier in 
               the sequence, then a(n) = product{k>=2} p(k-1)^b(n,k); If n does 
               not occur earlier in the sequence, then a(n) = {k>=1} p(k+1)^b(n,
               k).
%C A118306 Sequence is a permutation of the positive integers and it is its own 
               inverse permutation.
%H A118306 Leroy Quet, <a href="http://www.prism-of-spirals.net/">Home Page</a> 
               (listed in lieu of email address)
%p A118306 A064989 := proc(n) local a,ifs,p ; a := 1 ; ifs := ifactors(n)[2] ; for 
               p in ifs do if op(1,p) > 2 then a := a* prevprime(op(1,p))^op(2,p) 
               ; fi ; od; RETURN(a) ; end: A003961 := proc(n) local a,ifs,p ; a 
               := 1 ; ifs := ifactors(n)[2] ; for p in ifs do a := a* nextprime(op(1,
               p))^op(2,p) ; od; RETURN(a) ; end: A118306 := proc(nmin) local a,
               anxt,i,n ; a := [1] ; while nops(a) < nmin do n := nops(a)+1 ; if 
               n in a then anxt := A064989(n) ; else anxt := A003961(n) ; fi ; a 
               := [op(a),anxt] ; od; a ; end: A118306(100) ; - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), 
               Sep 06 2007
%Y A118306 Cf. A003961, A064989.
%Y A118306 Sequence in context: A061898 A021756 A084398 this_sequence A124003 A159588 
               A118045
%Y A118306 Adjacent sequences: A118303 A118304 A118305 this_sequence A118307 A118308 
               A118309
%K A118306 nonn
%O A118306 1,2
%A A118306 Leroy Quet May 14 2006
%E A118306 More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Sep 06 2007

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