A305898 - OEIS

%I #6 Jul 01 2018 08:35:46

%S 1,2,2,3,2,4,2,5,3,4,2,6,2,4,4,7,2,6,2,6,4,4,2,8,9,4,5,6,2,10,2,11,4,

%T 4,4,12,2,4,4,8,2,10,2,6,6,4,2,13,3,14,4,6,2,8,15,8,4,4,2,16,2,4,17,

%U 18,15,10,2,6,4,10,2,19,2,4,6,6,15,10,2,13,20,4,2,16,4,4,4,8,2,16,15,6,4,4,15,21,2,6,6,22,2,10,2,8,10

%N Filter sequence combining prime signature of n (A046523) and similar signature (A284011) obtained when Stern polynomial B(n,x) is factored over Z.

%C Restricted growth sequence transform of ordered pair [A046523(n), A284011(n)].

%C For all i, j: a(i) = a(j) => A305892(i) = A305892(j).

%H Antti Karttunen, <a href="/A305898/b305898.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 pfps(n) = { my(f=factor(n)); sum(i=1, #f~, f[i, 2] * 'x^(primepi(f[i, 1])-1)); };

%o A284010(n) = { if(!bitand(n, (n-1)), 0, my(p=0, f=vecsort(factor(pfps(n))[, 2], ,4)); prod(i=1, #f, (p=nextprime(p+1))^f[i])); }

%o A003961(n) = my(f = factor(n)); for (i=1, #f~, f[i, 1] = nextprime(f[i, 1]+1)); factorback(f); \\ From A003961

%o A260443(n) = if(n<2, n+1, if(n%2, A260443(n\2)*A260443(n\2+1), A003961(A260443(n\2))));

%o A284011(n) = A284010(A260443(n));

%o A046523(n) = { my(f=vecsort(factor(n)[, 2], , 4), p); prod(i=1, #f, (p=nextprime(p+1))^f[i]); };  \\ From A046523

%o Aux305898(n) = [A046523(n), A284011(n)];

%o v305898 = rgs_transform(vector(up_to, n, Aux305898(n)));

%o A305898(n) = v305898[n];

%Y Cf. A046523, A284011, A305892, A305899.

%Y Cf. also A305790.

%K nonn

%O 1,2

%A _Antti Karttunen_, Jul 01 2018