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 A260717 #12 Aug 02 2015 17:54:33 %S A260717 2,3,3,4,5,5,5,7,7,7,6,9,11,11,11,7,11,13,13,13,13,8,13,17,17,17,17, %T A260717 17,9,15,19,23,23,23,23,23,10,17,23,25,25,25,25,25,25,11,19,25,29,29, %U A260717 29,29,29,29,29,12,21,29,31,37,37,37,37,37,37,37,13,23,31,37,41,41,41,41,41,41,41,41,14,25,35,41,43,43,43,43,43,43,43,43,43 %N A260717 Square array: row n gives the numbers remaining before the stage n of Ludic sieve. %C A260717 This square array A(row,col) is read by downwards antidiagonals as: A(1,1), A(1,2), A(2,1), A(1,3), A(2,2), A(3,1), etc. %C A260717 Ludic sieve starts with natural numbers larger than one: 2, 3, 4, 5, 6, 7, ... and in each subsequent stage one sets k = <the initial term of the preceding row> (which will be one of Ludic numbers) and removes both k and every k-th term after it, from column positions 1, 1+k, 1+2k, 1+3k, etc. of the preceding row to produce the next row of this array. %H A260717 Antti Karttunen, <a href="/A260717/b260717.txt">Table of n, a(n) for n = 1..10440; the first 144 antidiagonals of the array</a> %H A260717 <a href="/index/Si#sieve">Index entries for sequences generated by sieves</a> %e A260717 The top left corner of the array: %e A260717 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 %e A260717 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33 %e A260717 5, 7, 11, 13, 17, 19, 23, 25, 29, 31, 35, 37, 41, 43, 47, 49 %e A260717 7, 11, 13, 17, 23, 25, 29, 31, 37, 41, 43, 47, 53, 55, 59, 61 %e A260717 11, 13, 17, 23, 25, 29, 37, 41, 43, 47, 53, 55, 61, 67, 71, 73 %e A260717 13, 17, 23, 25, 29, 37, 41, 43, 47, 53, 61, 67, 71, 73, 77, 83 %e A260717 17, 23, 25, 29, 37, 41, 43, 47, 53, 61, 67, 71, 77, 83, 89, 91 %e A260717 23, 25, 29, 37, 41, 43, 47, 53, 61, 67, 71, 77, 83, 89, 91, 97 %e A260717 25, 29, 37, 41, 43, 47, 53, 61, 67, 71, 77, 83, 89, 91, 97, 107 %e A260717 29, 37, 41, 43, 47, 53, 61, 67, 71, 77, 83, 89, 91, 97, 107, 115 %e A260717 37, 41, 43, 47, 53, 61, 67, 71, 77, 83, 89, 91, 97, 107, 115, 119 %e A260717 41, 43, 47, 53, 61, 67, 71, 77, 83, 89, 91, 97, 107, 115, 119, 121 %e A260717 43, 47, 53, 61, 67, 71, 77, 83, 89, 91, 97, 107, 115, 119, 121, 127 %e A260717 47, 53, 61, 67, 71, 77, 83, 89, 91, 97, 107, 115, 119, 121, 127, 131 %e A260717 53, 61, 67, 71, 77, 83, 89, 91, 97, 107, 115, 119, 121, 127, 131, 143 %e A260717 61, 67, 71, 77, 83, 89, 91, 97, 107, 115, 119, 121, 127, 131, 143, 149 %e A260717 etc. %o A260717 (Scheme) %o A260717 (define (A260717 n) (A260717bi (A002260 n) (A004736 n))) %o A260717 (define (A260717bi row col) ((rowfun_n_for_A003309sieve row) col)) %o A260717 (define (add1 n) (1+ n)) %o A260717 ;; Uses definec-macro which can memoize also function-closures: %o A260717 (definec (rowfun_n_for_A003309sieve n) (if (= 1 n) add1 (let* ((prevrowfun (rowfun_n_for_A003309sieve (- n 1))) (everynth (prevrowfun 1))) (compose-funs prevrowfun (nonzero-pos 1 1 (lambda (i) (modulo (- i 1) everynth))))))) %Y A260717 Transpose: A260718. %Y A260717 Column 1: A003309 (without the initial 1). %Y A260717 Row 1: A020725, Row 2: A144396, Row 3: A007310 (from its second term onward), Row 4: A260714, Row 5: A260715. %Y A260717 Cf. A255127 (gives the numbers removed at each stage). %Y A260717 Cf. also array A258207. %K A260717 nonn,tabl %O A260717 1,1 %A A260717 _Antti Karttunen_, Jul 30 2015