A005510 a(n) = 1 + a(floor(n/2))*a(ceiling(n/2)) for n > 1, a(1) = 3.

3, 10, 31, 101, 311, 962, 3132, 10202, 31412, 96722, 299183, 925445, 3012985, 9809425, 31952665, 104080805, 320465225, 986713745, 3038231465, 9355145285, 28937578127, 89510467490, 276877411436, 856448448026, 2788351903326, 9078078610226, 29555650383626

Offset: 1

Author

Colin Mallows

Keywords

• nonn
• easy

Comments

All terms are congruent to 3 mod 7.

References

• N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Cf. A005468, A005469.

Programs

Maple

a:= proc(n) option remember; `if`(n=1, 3,
      1+(t->a(t)*a(n-t))(iquo(n, 2)))
    end:
seq(a(n), n=1..30);  # Alois P. Heinz, Jul 04 2019