Search: id:A152455
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%I A152455
%S A152455 0,1,2,2,4,2,6,4,6,4,10,4,12,6,6,8,16,6,18,6,8,10,22,6,20,12,18,8,28,6,
%T A152455 30,16,12,16,10,8,36,18,14,8,40,8,42,12,10,22,46,10,42,20,18,14,52,18,
%U A152455 14,10,20,28,58,8,60,30,12,32,16,12,66,18,24,10,70,10,72,36,22,20,16,14
%N A152455 a(n) = minimal integer m such that there exists an m X m integer matrix 
               of order n.
%F A152455 a(1)=0, a(2)=1. If n mod 4 eq 2 then a(n)=a(n/2).
%F A152455 Otherwise a(n) = sum (pi-1)*pi^(ei-1) where n = p1^e1*p2^e2*...pk^ek 
               is prime factorization of n.
%o A152455 (MAGMA) a := function(n)
%o A152455 if n le 2 then return n-1; end if;
%o A152455 if n mod 4 eq 2 then n := n div 2; end if;
%o A152455 f := Factorization(n);
%o A152455 return &+[(t[1]-1)*t[1]^(t[2]-1):t in f];
%o A152455 end function;
%Y A152455 See A080737 for another version. - N. J. A. Sloane (njas(AT)research.att.com), 
               Dec 05 2008
%Y A152455 Sequence in context: A096504 A011773 A080737 this_sequence A000010 A003978 
               A122645
%Y A152455 Adjacent sequences: A152452 A152453 A152454 this_sequence A152456 A152457 
               A152458
%K A152455 easy,nonn
%O A152455 1,3
%A A152455 W. R. Unger (billu(AT)maths.usyd.edu.au), Dec 04 2008

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