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 A117942 #14 Jul 27 2017 14:27:27 %S A117942 1,-1,-2,-1,1,2,-2,2,4,-1,1,2,1,-1,-2,2,-2,-4,-2,2,4,2,-2,-4,4,-4,-8, %T A117942 -1,1,2,1,-1,-2,2,-2,-4,1,-1,-2,-1,1,2,-2,2,4,2,-2,-4,-2,2,4,-4,4,8, %U A117942 -2,2,4,2,-2,-4,4,-4,-8,2,-2,-4,-2,2,4,-4,4,8,4,-4,-8,-4,4,8,-8,8,16,-1,1,2,1,-1,-2,2,-2,-4,1,-1 %N A117942 a(n) = a(3n) = -a(3n+1) = -a(3n+2)/2. %C A117942 a(n) = a(3n)/a(0) = a(3n+1)/a(1) = a(3n+2)/a(2). %C A117942 Row sums of A117941. %H A117942 Antti Karttunen, <a href="/A117942/b117942.txt">Table of n, a(n) for n = 0..19683</a> %F A117942 a(n) = 2^A081603(n) * (-1)^(A062756(n)+A081603(n)). - _Antti Karttunen_, Jul 26 2017 %o A117942 (Scheme) %o A117942 ;; A stand-alone recurrence: %o A117942 (define (A117942 n) (cond ((zero? n) 1) ((zero? (modulo n 3)) (A117942 (/ n 3))) (else (let ((d (modulo n 3))) (- (* d (A117942 (/ (- n d) 3)))))))) %o A117942 ;; An implementation based on a new formula: %o A117942 (Scheme) (define (A117942 n) (* (A000079 (A081603 n)) (expt -1 (+ (A062756 n) (A081603 n))))) %o A117942 ;; _Antti Karttunen_, Jul 26 2017 %Y A117942 Cf. A117592 (gives the absolute values). %Y A117942 Cf. A062756, A081603. %K A117942 sign %O A117942 0,3 %A A117942 _Paul Barry_, Apr 05 2006 %E A117942 More terms from _Antti Karttunen_, Jul 26 2017