|
| |
|
|
A155883
|
|
The sequence gives the three-dimensional forms of the centred hexagonal numbers. Two examples: its third term 173 is built 19 + 37 + 61 + 37 + 19 and its fourth term 505 is built 37 + 61 + 91 + 127 + 91 + 61 + 37.
|
|
0
| | |
|
|
|
OFFSET
| 1,2
|
|
|
COMMENTS
| The sequence's digital roots run recursively 1, 6, 2.
|
|
|
REFERENCES
| David Z Crookes, De Pulchritudine Numerorum Figuratorum, in Mathematics in School (May, 1988), 38-39.
|
|
|
FORMULA
| 14n cubed minus 30n squared plus 24n minus 7
|
|
|
EXAMPLE
| For n = 3 the solution is [14 x 27] - [30 x 9] + [24 x 3] - 7 = 173
|
|
|
CROSSREFS
| Sequence in context: A172077 A180943 A113752 * A071914 A046142 A135827
Adjacent sequences: A155880 A155881 A155882 * A155884 A155885 A155886
|
|
|
KEYWORD
| nonn
|
|
|
AUTHOR
| David Z Crookes (davidzcrookes(AT)btinternet.com), Jan 29 2009
|
| |
|
|
