A393527 a(0) = a(1) = a(2) = 1; thereafter odd indexed terms are the sum of the last 3 terms and even indexed terms are the sum of all previous terms.

1, 1, 1, 3, 6, 10, 22, 38, 82, 142, 306, 530, 1142, 1978, 4262, 7382, 15906, 27550, 59362, 102818, 221542, 383722, 826806, 1432070, 3085682, 5344558, 11515922, 19946162, 42978006, 74440090, 160396102, 277814198, 598606402, 1036816702, 2234029506, 3869452610

Offset

0,4

Links

Table of n, a(n) for n=0..35.

James S. DeArmon, R Code for A393527

Formula

a(n) = a(n-1) + a(n-2) + a(n-3) for odd n >= 3;

a(n) = Sum_{k=1..n-1} a(k) for even n >= 4.

Mathematica

s={1, 1, 1}; Do[AppendTo[s, s[[-3]]+s[[-2]]+s[[-1]]]; AppendTo[s, Total[s]], {i, 17}]; s (* James C. McMahon, Feb 27 2026 *)

Prog

(R) # See link.

Crossrefs

Cf. A062112, A000213.

Sequence in context: A362909 A282515 A284202 * A275189 A091616 A117224

Adjacent sequences: A393524 A393525 A393526 * A393528 A393529 A393530

Keyword

nonn

Author

James S. DeArmon, Feb 18 2026

Status

approved