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A320115 Filter sequence for counting the residue classes mod 4 of divisors of n.

%I A320115 #9 Oct 08 2018 08:09:39
%S A320115 1,2,3,4,5,6,3,7,8,9,3,10,5,6,11,12,5,13,3,14,11,6,3,15,16,9,11,10,5,
%T A320115 17,3,18,11,9,11,19,5,6,11,20,5,17,3,10,21,6,3,22,8,23,11,14,5,17,11,
%U A320115 15,11,9,3,24,5,6,25,26,27,17,3,14,11,17,3,28,5,9,25,10,11,17,3,29,30,9,3,24,27,6,11,15,5,31,11,10,11,6,11,32,5,13,25,33,5,17,3,20
%N A320115 Filter sequence for counting the residue classes mod 4 of divisors of n.
%C A320115 Restricted growth sequence transform of A320114.
%C A320115 For all i, j:
%C A320115   A319994(i) = A319994(j) => a(i) = a(j),
%C A320115   A320004(i) = A320004(j) => a(i) = a(j),
%C A320115   a(i) = a(j) => A002654(i) = A002654(j).
%H A320115 Antti Karttunen, <a href="/A320115/b320115.txt">Table of n, a(n) for n = 1..100000</a>
%o A320115 (PARI)
%o A320115 up_to = 100000;
%o A320115 A320114(n) = { my(m=1); fordiv(n,d,if(d>1, m *= prime(1+(d%4)))); (m); };
%o A320115 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 A320115 v320115 = rgs_transform(vector(up_to,n,A320114(n)));
%o A320115 A320115(n) = v320115[n];
%Y A320115 Cf. A319994, A320004, A320109, A320113, A320114, A320117.
%K A320115 nonn
%O A320115 1,2
%A A320115 _Antti Karttunen_, Oct 06 2018