A047931 Number of new penny-penny contacts when putting pennies on a table following a spiral pattern.

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, 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, 3, 3, 2, 3, 3, 3, 3, 2, 3, 3, 3, 3, 2, 3, 3, 3, 3, 2, 3, 3, 3, 3, 3

Offset

1,3

Links

Table of n, a(n) for n=1..91.

R. W. Grosse-Kunstleve, Penny Spiral Sequence

Formula

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.

Example

From Omar E. Pol, Nov 16 2016: (Start)
The sequence written as a spiral begins:
.
.                2 - 3 - 3 - 3 - 3 - 2
.               /                     \
.              3   2 - 3 - 3 - 3 - 2   3
.             /   /                 \   \
.            3   3   2 - 3 - 3 - 2   3   3
.           /   /   /             \   \   \
.          3   3   3   2 - 3 - 2   3   3   3
.         /   /   /   /         \   \   \   \
.        3   3   3   3   2 - 2   3   3   3   3
.       /   /   /   /   /     \   \   \   \   \
.      2   2   2   2   2   0 - 1   2   2   2   2
.       \   \   \   \   \         /   /   /   /
.        3   3   3   3   2 - 3 - 2   3   3   3
.         \   \   \   \             /   /   /
.          3   3   3   2 - 3 - 3 - 2   3   3
.           \   \   \                 /   /
.            3   3   2 - 3 - 3 - 3 - 2   3
.             \   \                     /
.              3   2 - 3 - 3 - 3 - 3 - 2
.               \
.                2 - 3 - 3 - 3 - 3 - 3
(End)

Crossrefs

Cf. A047932.

Sequence in context: A351284 A268317 A234092 * A258571 A033618 A061357

Adjacent sequences: A047928 A047929 A047930 * A047932 A047933 A047934

Keyword

nonn

Author

Ralf W. Grosse-Kunstleve

Status

approved