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 A225378 #21 Feb 11 2015 23:11:51 %S A225378 2,3,7,8,10,12,13,14,15,17,18,19,21,22,23,25,26,27,28,29,30,31,32,33, %T A225378 35,37,38,39,40,41,42,43,44,45,47,48,49,50,51,52,53,54,55,56,57,58,61, %U A225378 62,63,64 %N A225378 Construct sequences P,Q,R by the rules: Q = first differences of P, R = second differences of P, P starts with 1,5,11, Q starts with 4,6, R starts with 2; at each stage the smallest number not yet present in P,Q,R is appended to R; every number appears exactly once in the union of P,Q,R. Sequence gives R. %C A225378 P can be extended for 10^6 terms, but it is not known if P,Q,R can be extended to infinity. %C A225378 A probabilistic argument suggests that P, Q, R are infinite. - _N. J. A. Sloane_, May 19 2013 %H A225378 Christopher Carl Heckman, <a href="/A225378/b225378.txt">Table of n, a(n) for n = 1..10000</a> %e A225378 The initial terms of P, Q, R are: %e A225378 1 5 11 20 36 60 94 140 199 272 360 %e A225378 4 6 9 16 24 34 46 59 73 88 %e A225378 2 3 7 8 10 12 13 14 15 %p A225378 See A225376. %Y A225378 Cf. A225376, A225377, A005228, A030124, A037257. %K A225378 nonn %O A225378 1,1 %A A225378 _N. J. A. Sloane_, May 12 2013, based on email from _Christopher Carl Heckman_, May 06 2013 %E A225378 Corrected and edited by _Christopher Carl Heckman_, May 12 2013