A080817 Leading diagonal of triangle in A080818.

1, 3, 6, 10, 6, 10, 15, 8, 13, 19, 26, 15, 22, 30, 16, 24, 33, 43, 25, 35, 46, 25, 36, 48, 61, 36, 49, 63, 35, 49, 64, 33, 48, 64, 81, 46, 63, 81, 43, 61, 80, 100, 58, 78, 99, 54, 75, 97, 49, 71, 94, 118, 66, 90, 115, 60, 85, 111, 138, 79, 106, 134, 72, 100, 129, 159, 93, 123

Offset

1,2

Links

Table of n, a(n) for n=1..68.

Formula

From David Wasserman, May 13 2004: (Start)

a(n) = (ceiling(sqrt(n(n+1)/2)))^2 - n(n-1)/2.

a(n) = A048761(A000217(n)) - A000217(n-1). (End)

Crossrefs

Cf. A080818, A080819, A080820.

Sequence in context: A065234 A333531 A082184 * A139762 A055262 A353199

Adjacent sequences: A080814 A080815 A080816 * A080818 A080819 A080820

Keyword

nonn

Author

Amarnath Murthy, Mar 21 2003

Extensions

More terms from David Wasserman, May 13 2004

Status

approved