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 A056233 #8 Jul 13 2013 12:02:32 %S A056233 9,17,26,33,40,47,52,57,65,74,80,85,95,110,122,129,136,143,148,156, %T A056233 169,179,185,191,196,202,210,216,220,225,232,239,244,249,257,266,272, %U A056233 277,287,300,308,312,318,326,332,337,343,349,357,369,382 %N A056233 Form an array with 3 rows: row 1 begins with 1; all rows are increasing; each entry is sum of 2 entries above it; each number appears at most once; smallest unused number is appended to first row if possible. Sequence gives row 3. %H A056233 Reinhard Zumkeller, <a href="/A056233/b056233.txt">Table of n, a(n) for n = 1..10000</a> %e A056233 Array begins %e A056233 1 2 4 7 8 10 12 ... %e A056233 .3 6 11 15 18 ... %e A056233 . 9 17 26 33 ... %o A056233 (Haskell) cf. A056231. %Y A056233 Cf. A056231, A056232, A056234. See also A057153, A052474, A057154, A056230. %K A056233 nonn,nice,easy %O A056233 1,1 %A A056233 _N. J. A. Sloane_, E. M. Rains, Aug 22 2000