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 A278528 #33 May 24 2025 21:43:22 %S A278528 0,1,0,1,2,1,0,1,3,1,2,1,0,1,4,1,2,1,0,1,3,1,2,1,5,1,0,1,2,1,6,1,3,1, %T A278528 2,1,4,1,0,1,2,1,7,1,3,1,2,1,0,1,5,1,2,1,4,1,3,1,2,1,8,1,0,1,2,1,9,1, %U A278528 3,1,2,1,6,1,4,1,2,1,0,1,3,1,2,1,5,1,10,1,2,1,0,1,3,1,2,1,4,1,7,1,2,1,11,1,3,1,2,1,0,1,5,1,2,1,4,1,3,1,2,1 %N A278528 a(n) = number of the round in which n is removed in the Flavius sieve, 0 if it is never removed (when n is one of the terms of A000960). %C A278528 a(n) = index of the row where n is located in array A278507, 0 if n does not occur there (when n is one of the terms of A000960). %H A278528 Antti Karttunen, <a href="/A278528/b278528.txt">Table of n, a(n) for n = 1..10707</a> %H A278528 <a href="/index/J#Josephus">Index entries for sequences related to the Josephus Problem</a> %F A278528 Conjecture: a(n) = [C > 0] * C where we start with A := n, B := n - 1, C, m := 0 and until A = B consecutively apply m := m + 1, C := A - B, A := abs(A - m - (A mod m)), B := abs(B - m - (B mod m)). - _Mikhail Kurkov_, May 19 2025 %o A278528 (Scheme) %o A278528 ;; Very crude. Find it with two nested loops. (Maybe a closed form exists?) %o A278528 (define (A278528 n) (cond ((not (zero? (A278169 n))) 0) ((even? n) 1) (else (let searchrow ((row 2)) (let searchcol ((col 1)) (cond ((>= (A278507bi row col) n) (if (= (A278507bi row col) n) row (searchrow (+ 1 row)))) (else (searchcol (+ 1 col))))))))) %o A278528 ;; Code for A278507bi given in A278507. %Y A278528 Cf. A278507, A278529 (the other index), A278538. %Y A278528 Cf. A000960 (positions of zeros). %K A278528 nonn %O A278528 1,5 %A A278528 _Antti Karttunen_, Nov 23 2016