1,2

Partial sums of A137681 prefaced with a 1 = left border of triangle A137680: (1, 1, 3, 7, 17, 40, 96, 228,...) = A137682. A variation of A137681 = column 2 of triangle A137680: (1, 0, 2, 4, 10, 23, 56, 132, 316,...).

Table of n, a(n) for n=1..14.

a(4) = 10 = sum of row 4 terms of triangle A137680: (7 + 2 + 0 + 1).

Cf. A137680, A137682.

Sequence in context: A210460 A191693 A238436 * A127389 A152173 A032171

Adjacent sequences: A137678 A137679 A137680 * A137682 A137683 A137684

nonn

Gary W. Adamson, Feb 05 2008

approved