A319346 - OEIS

%I #5 Sep 24 2018 17:46:38

%S 1,2,3,4,3,5,3,6,7,8,3,9,3,10,11,12,3,13,3,14,15,16,3,17,18,19,20,21,

%T 3,22,3,23,24,25,20,26,3,27,28,29,3,30,3,31,32,33,3,34,35,36,37,38,3,

%U 39,28,40,41,42,3,43,3,44,45,46,47,48,3,49,50,51,3,52,3,53,54,55,47,56,3,57,58,59,3,60,41,61,32,62,3,63,37,64,65,66,67,68,3,69

%N Filter sequence combining the sum of proper divisors (A001065) with the 2-adic valuation of n (A007814).

%C Restricted growth sequence transform of ordered pair [A001065(n), A007814(n)].

%H Antti Karttunen, <a href="/A319346/b319346.txt">Table of n, a(n) for n = 1..65537</a>

%o (PARI)

%o up_to = 65537;

%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 A001065(n) = (sigma(n)-n);

%o A007814(n) = valuation(n,2);

%o v319346 = rgs_transform(vector(up_to,n,[A001065(n),A007814(n)]));

%o A319346(n) = v319346[n];

%Y Cf. A001065, A007814, A305801, A319338.

%K nonn

%O 1,2

%A _Antti Karttunen_, Sep 24 2018