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A286358 Compound filter: a(n) = P(A286357(n), A161942(n)), where P(n,k) is sequence A000027 used as a pairing function. 5

%I #11 May 10 2017 17:46:08

%S 1,4,6,22,8,13,10,106,79,47,13,39,30,19,19,466,47,742,24,233,21,58,19,

%T 139,466,233,32,49,122,70,21,1954,26,380,26,4096,192,139,49,1037,233,

%U 34,81,256,782,70,26,531,1597,4279,70,1227,380,157,70,157,41,1037,139,280,498,34,124,8002,256,83,174,2018,34,83,70,18916,705,1655,531,669,34,280,41

%N Compound filter: a(n) = P(A286357(n), A161942(n)), where P(n,k) is sequence A000027 used as a pairing function.

%C Partitions natural numbers to the same equivalence classes as A000203. That is, for all i, j: a(i) = a(j) <=> A000203(i) = A000203(j). This follows because both A161942(n) and A286357(n) can be (are) defined as functions of A000203, and on the other hand, A000203(n) can be uniquely reconstructed from A161942(n) and A286357(n), thus from a(n).

%H Antti Karttunen, <a href="/A286358/b286358.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>

%H <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a>

%F a(n) = (1/2)*(2 + ((A286357(n)+A161942(n))^2) - A286357(n) - 3*A161942(n)).

%o (PARI)

%o A001511(n) = (1+valuation(n,2));

%o A000265(n) = (n >> valuation(n, 2));

%o A161942(n) = A000265(sigma(n));

%o A286357(n) = A001511(sigma(n));

%o A286358(n) = (1/2)*(2 + ((A286357(n)+A161942(n))^2) - A286357(n) - 3*A161942(n));

%o for(n=1, 10000, write("b286358.txt", n, " ", A286358(n)));

%o (Scheme) (define (A286358 n) (* (/ 1 2) (+ (expt (+ (A286357 n) (A161942 n)) 2) (- (A286357 n)) (- (* 3 (A161942 n))) 2)))

%Y Cf. A000027, A000203, A161942, A286034, A286260, A286357, A286359, A286360, A286460.

%K nonn

%O 1,2

%A _Antti Karttunen_, May 10 2017

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Last modified March 29 08:13 EDT 2024. Contains 371265 sequences. (Running on oeis4.)