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 A130556 #2 Mar 31 2012 20:55:21 %S A130556 1,11,1,111,1,11,1111,11,1,111,11111,111,1,11,1111,111111,1111,11,1, %T A130556 111,11111,1111111,11111,111,1,11,1111,111111,11111111,111111,1111,11, %U A130556 1,111,11111,1111111 %N A130556 A model of the atomic nucleus (Shell model of nucleus). A triangle. %C A130556 1 is equal to 2 protons, 11 is equal to 2+2 protons, 111 is equal to 2+2+2 protons... %C A130556 Repunit numbers represent the subshells. %e A130556 A geometric model of the shell structure of nucleus: %e A130556 ...|----------------------.i.----------------------| %e A130556 ...|...|------------------.h.------------------|...| %e A130556 ...|...|...|--------------.g.--------------|...|...| %e A130556 ...|...|...|...|----------.f.----------|...|...|...| %e A130556 ...|...|...|...|...|------.d.------|...|...|...|...| %e A130556 ...|...|...|...|...|...|--.p.--|...|...|...|...|...| %e A130556 ...|...|...|...|...|...|...s...|...|...|...|...|...| %e A130556 ...|...|...|...|...|...|...|...|...|...|...|...|...| %e A130556 ...|...|...|...|...|...|.......|...|...|...|...|...| %e A130556 ...|...|...|...|...|.......1.......|...|...|...|...| %e A130556 ...|...|...|...|......11.......1.......|...|...|...| %e A130556 ...|...|...|......111......1......11.......|...|...| %e A130556 ...|...|.....1111.....11.......1......111......|...| %e A130556 ...|.....11111....111......1......11.....1111......| %e A130556 ....111111...1111.....11.......1......111....11111.... %e A130556 1111111..11111....111......1......11.....1111...111111 %e A130556 ...................................................... %e A130556 ...|...|...|...|...|...|...|...|...|...|...|...|...| %e A130556 ...|...|...|...|...|...|...|1/2|...|...|...|...|...| %e A130556 ...|...|...|...|...|...|----3/2----|...|...|...|...| %e A130556 ...|...|...|...|...|--------5/2--------|...|...|...| %e A130556 ...|...|...|...|------------7/2------------|...|...| %e A130556 ...|...|...|----------------9/2----------------|...| %e A130556 ...|...|-------------------11/2--------------------| %e A130556 ...|----------------------.13/2.-------------------- %Y A130556 Cf. A056951, A130517, A130598, A130602. %K A130556 nonn,tabl %O A130556 1,2 %A A130556 _Omar E. Pol_, Aug 09 2007, Aug 12 2007