A293224 - OEIS

%I #8 Oct 18 2017 00:56:12

%S 1,1,1,2,1,2,1,2,1,3,1,4,1,4,2,5,1,4,1,3,6,3,1,7,2,2,1,5,1,7,1,7,2,5,

%T 4,8,1,9,1,10,1,11,1,12,4,12,1,13,6,14,4,14,1,8,3,15,16,3,1,17,1,2,18,

%U 15,2,11,1,7,9,19,1,20,1,2,21,12,4,11,1,22,1,3,1,23,5,4,2,22,1,24,6,25,1,12,9,26,1,14,4,27,1,13,1,28,23,14,1,29,1,30

%N Restricted growth sequence transform of A293222, a product formed from the 2-digits present in the ternary expansions of proper divisors of n.

%H Antti Karttunen, <a href="/A293224/b293224.txt">Table of n, a(n) for n = 1..19683</a>

%o (PARI)

%o rgs_transform(invec) = { my(om = Map(), outvec = vector(length(invec)), u=1); for(i=1, length(invec), if(mapisdefined(om,invec[i]), my(pp = mapget(om, invec[i])); outvec[i] = outvec[pp] , mapput(om,invec[i],i); outvec[i] = u; u++ )); outvec; };

%o write_to_bfile(start_offset,vec,bfilename) = { for(n=1, length(vec), write(bfilename, (n+start_offset)-1, " ", vec[n])); }

%o A019565(n) = {my(j,v); factorback(Mat(vector(if(n, #n=vecextract(binary(n), "-1..1")), j, [prime(j), n[j]])~))}; \\ This function from _M. F. Hasler_

%o A289814(n) = { my (d=digits(n, 3)); fromdigits(vector(#d, i, if (d[i]==2, 1, 0)), 2); } \\ From _Remy Sigrist_

%o A293222(n) = { my(m=1); fordiv(n,d,if(d < n,m *= A019565(A289814(d)))); m; };

%o write_to_bfile(1,rgs_transform(vector(19683,n,A293222(n))),"b293224.txt");

%Y Cf. A293222.

%Y Cf. also A290092, A293223, A293215, A293217, A293232, A293225, A293226.

%K nonn

%O 1,4

%A _Antti Karttunen_, Oct 03 2017