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

Author

Amarnath Murthy, Mar 21 2003

Keywords

• nonn

Crossrefs

Cf. A080818, A080819, A080820.

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)

Extensions

More terms from David Wasserman, May 13 2004