A047931 - OEIS

%I #16 Apr 10 2018 08:28:07

%S 0,1,2,2,2,2,3,2,2,3,2,3,2,3,2,3,2,3,3,2,3,2,3,3,2,3,3,2,3,3,2,3,3,2,

%T 3,3,3,2,3,3,2,3,3,3,2,3,3,3,2,3,3,3,2,3,3,3,2,3,3,3,3,2,3,3,3,2,3,3,

%U 3,3,2,3,3,3,3,2,3,3,3,3,2,3,3,3,3,2,3,3,3,3,3

%N Number of new penny-penny contacts when putting pennies on a table following a spiral pattern.

%H R. W. Grosse-Kunstleve, <a href="http://web.archive.org/web/20050425075654/http://cci.lbl.gov/~rwgk/EIS/PennySpiral.html">Penny Spiral Sequence</a>

%F The n-th "chunk" consists of 2 3{n-2} 2 3{n-1} 2 3{n-1} 2 3{n-1} 2 3{n-1} 2 3{n}, where a{b} symbolizes b repetitions of a.

%e From _Omar E. Pol_, Nov 16 2016: (Start)

%e The sequence written as a spiral begins:

%e .

%e .                2 - 3 - 3 - 3 - 3 - 2

%e .               /                     \

%e .              3   2 - 3 - 3 - 3 - 2   3

%e .             /   /                 \   \

%e .            3   3   2 - 3 - 3 - 2   3   3

%e .           /   /   /             \   \   \

%e .          3   3   3   2 - 3 - 2   3   3   3

%e .         /   /   /   /         \   \   \   \

%e .        3   3   3   3   2 - 2   3   3   3   3

%e .       /   /   /   /   /     \   \   \   \   \

%e .      2   2   2   2   2   0 - 1   2   2   2   2

%e .       \   \   \   \   \         /   /   /   /

%e .        3   3   3   3   2 - 3 - 2   3   3   3

%e .         \   \   \   \             /   /   /

%e .          3   3   3   2 - 3 - 3 - 2   3   3

%e .           \   \   \                 /   /

%e .            3   3   2 - 3 - 3 - 3 - 2   3

%e .             \   \                     /

%e .              3   2 - 3 - 3 - 3 - 3 - 2

%e .               \

%e .                2 - 3 - 3 - 3 - 3 - 3

%e (End)

%Y Cf. A047932.

%K nonn

%O 1,3

%A _Ralf W. Grosse-Kunstleve_