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A152455 a(n) = minimal integer m such that there exists an m X m integer matrix of order n. 2

%I

%S 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,

%T 6,30,16,12,16,10,8,36,18,14,8,40,8,42,12,10,22,46,10,42,20,18,14,52,

%U 18,14,10,20,28,58,8,60,30,12,32,16,12,66,18,24,10,70,10,72,36,22,20,16,14

%N a(n) = minimal integer m such that there exists an m X m integer matrix of order n.

%F a(1)=0, a(2)=1. If n mod 4 eq 2 then a(n)=a(n/2).

%F Otherwise a(n) = sum (pi-1)*pi^(ei-1) where n = p1^e1*p2^e2*...pk^ek is prime factorization of n.

%o (MAGMA) a := function(n)

%o if n le 2 then return n-1; end if;

%o if n mod 4 eq 2 then n := n div 2; end if;

%o f := Factorization(n);

%o return &+[(t[1]-1)*t[1]^(t[2]-1):t in f];

%o end function;

%Y See A080737 for another version. - _N. J. A. Sloane_, Dec 05 2008

%K easy,nonn

%O 1,3

%A W. R. Unger (billu(AT)maths.usyd.edu.au), Dec 04 2008

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Last modified February 16 21:59 EST 2019. Contains 320200 sequences. (Running on oeis4.)