A065221 Fill a triangular array by rows by writing numbers 1 up to b(0), 1 up to b(1), etc., where b(n) are the pentagonal numbers. The final elements of the rows form a(n).

1, 2, 5, 4, 9, 3, 10, 18, 5, 15, 26, 3, 16, 30, 45, 10, 27, 45, 64, 14, 35, 57, 80, 12, 37, 63, 90, 1, 30, 60, 91, 123, 11, 45, 80, 116, 153, 15, 54, 94, 135, 177, 10, 54, 99, 145, 192, 240, 42, 92, 143, 195, 248, 15, 70, 126, 183, 241, 300, 30, 91, 153, 216, 280, 345, 35

Offset

0,2

Links

Table of n, a(n) for n=0..65.

Example

The array begins
....1
...1.2
..3.4.5
.1.2.3.4
5.6.7.8.9

Crossrefs

Cf. A000326.

Mini-index to these sequences: A064766, A064865, A064866, A065221-A655234 are all of the same type. See A064766 for a detailed explanation.

Sequence in context: A198193 A316905 A214533 * A373053 A283419 A114752

Adjacent sequences: A065218 A065219 A065220 * A065222 A065223 A065224

Keyword

easy,nonn

Author

Floor van Lamoen, Oct 22 2001

Status

approved