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 A286463 Compound filter (3-adic valuation & prime-signature): a(n) = P(A051064(n), A046523(n)), where P(n,k) is sequence A000027 used as a pairing function. 5

%I

%S 1,2,5,7,2,23,2,29,18,16,2,80,2,16,23,121,2,94,2,67,23,16,2,302,7,16,

%T 59,67,2,467,2,497,23,16,16,706,2,16,23,277,2,467,2,67,94,16,2,1178,7,

%U 67,23,67,2,355,16,277,23,16,2,1832,2,16,94,2017,16,467,2,67,23,436,2,2704,2,16,80,67,16,467,2,1129,195,16,2,1832,16,16,23,277,2,1894,16

%N Compound filter (3-adic valuation & prime-signature): a(n) = P(A051064(n), A046523(n)), where P(n,k) is sequence A000027 used as a pairing function.

%H Antti Karttunen, <a href="/A286463/b286463.txt">Table of n, a(n) for n = 1..10000</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/PairingFunction.html">Pairing Function</a>

%F a(n) = (1/2)*(2 + ((A051064(n)+A046523(n))^2) - A051064(n) - 3*A046523(n)).

%o (PARI)

%o A051064(n) = if(n<1, 0, 1+valuation(n, 3));

%o A046523(n) = { my(f=vecsort(factor(n)[, 2], , 4), p); prod(i=1, #f, (p=nextprime(p+1))^f[i]); }; \\ This function from _Charles R Greathouse IV_, Aug 17 2011

%o A286463(n) = (1/2)*(2 + ((A051064(n)+A046523(n))^2) - A051064(n) - 3*A046523(n));

%o for(n=1, 10000, write("b286463.txt", n, " ", A286463(n)));

%o (Scheme) (define (A286463 n) (* (/ 1 2) (+ (expt (+ (A051064 n) (A046523 n)) 2) (- (A051064 n)) (- (* 3 (A046523 n))) 2)))

%o (Python)

%o from sympy import factorint, divisors, divisor_count, mobius

%o def a051064(n): return -sum([mobius(3*d)*divisor_count(n/d) for d in divisors(n)])

%o def P(n):

%o f = factorint(n)

%o return sorted([f[i] for i in f])

%o def a046523(n):

%o x=1

%o while True:

%o if P(n) == P(x): return x

%o else: x+=1

%o def T(n, m): return ((n + m)**2 - n - 3*m + 2)/2

%o def a(n): return T(a051064(n), a046523(n)) # _Indranil Ghosh_, May 11 2017

%Y Cf. A000027, A046523, A051064, A286161, A286461, A286462, A286464.

%K nonn

%O 1,2

%A _Antti Karttunen_, May 10 2017

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Last modified May 9 06:14 EDT 2021. Contains 343692 sequences. (Running on oeis4.)