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Squarefree parts of products of numbers of faces of Platonic solids.
1

%I #8 Feb 03 2015 09:20:08

%S 1,6,2,3,1,5,6,2,1,3,1,2,5,6,30,2,1,10,3,6,15,1,2,5,6,1,3,30,2,1,10,5,

%T 3,6,15,1,2,5,1,10,6,1,3,30,2,1,6,10,2,5,3,2,6,15,1,30,2,3,5,1,10,6,1,

%U 3,30,6,5,2,15,1,6,10,2,5,3,2,6,1,15,3,1

%N Squarefree parts of products of numbers of faces of Platonic solids.

%F a(n) = A007913(A062554(n)). - _Michel Marcus_, Feb 03 2015

%e 32 is the eighth smallest number expressible as a product of members of {4,6,8,12,20}, namely as 4x8. The largest square divisor of 32 is 16. 32/16=2, so a(8)=2.

%o (PARI) ismult(n, v, vp) = {for (k=1, #v, q = n/v[k]; if ((type(q)== "t_INT") && vecsearch(vp, q), return (1)););}

%o lista(nn) = {v = [4,6,8,12,20]; vp = []; for (n=2, nn, if (vecsearch(v, n) || ismult(n, v, vp), print1(core(n), ", "); vp = concat(vp, n);););} \\ _Michel Marcus_, Feb 03 2015

%Y Cf. A062554.

%K nonn

%O 1,2

%A _Neil Fernandez_, Jul 04 2001

%E More terms from _Michel Marcus_, Feb 03 2015