This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A289621 #15 Jul 18 2017 11:46:01 %S A289621 0,1,1,2,1,5,1,4,2,5,1,8,1,5,5,7,1,8,1,8,5,5,1,12,2,5,4,8,1,13,1,11,5, %T A289621 5,5,12,1,5,5,12,1,13,1,8,8,5,1,17,2,8,5,8,1,12,5,12,5,5,1,18,1,5,8, %U A289621 16,5,13,1,8,5,13,1,17,1,5,8,8,5,13,1,17,7,5,1,18,5,5,5,12,1,18,5,8,5,5,5,23,1,8,8 %N A289621 Compound filter (omega & bigomega): a(1) = 0, for n > 1, a(n) = P(A001221(n), A001222(n)), where P(n,k) is sequence A000027 used as a pairing function. %H A289621 Antti Karttunen, <a href="/A289621/b289621.txt">Table of n, a(n) for n = 1..10000</a> %H A289621 <a href="/index/Eu#epf">Index entries for sequences computed from exponents in factorization of n</a> %F A289621 a(1) = 0, for n > 1, a(n) = (1/2)*(2 + ((A001221(n)+A001222(n))^2) - A001221(n) - 3*A001222(n)). %o A289621 (PARI) A289621(n) = if(1==n,0,(1/2)*(2 + ((omega(n)+bigomega(n))^2) - omega(n) - 3*bigomega(n))); %o A289621 (Scheme) (define (A289621 n) (if (= 1 n) 0 (* (/ 1 2) (+ (expt (+ (A001221 n) (A001222 n)) 2) (- (A001221 n)) (- (* 3 (A001222 n))) 2)))) %Y A289621 Cf. A000027, A046523. %Y A289621 Cf. A001221, A001222, A008966, A046660, A070012, A070013, A070014, A088529, A088530, A181591 (sequences with matching equivalence classes). %K A289621 nonn %O A289621 1,4 %A A289621 _Antti Karttunen_, Jul 16 2017