A272038 Somos's sequence {b(9,n)} defined in comment in A078495: a(0)=a(1)=...=a(20)=1; for n>=21, a(n)=(a(n-1)*a(n-20)+a(n-10)*a(n-11))/a(n-21).

1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 19, 31, 51, 81, 123, 179, 251, 341, 451, 1045, 1691, 2451, 3459, 4977, 7467, 11679, 18755, 30349, 48763, 100474, 282777, 679512, 1391391, 2547414, 4327101

Offset

0,22

Links

Seiichi Manyama, Table of n, a(n) for n = 0..578

Prog

(Ruby)
def b(k, n)
  b = Array.new(2 * k + 3, 1)
  (2 * k + 3..n).each{|i|
    j = (b[i - 1] * b[i - 2 * k - 2] + b[i - k - 1] * b[i - k - 2]) / b[i - 2 * k - 3].to_r
    j = j.to_i if j.denominator == 1
    b[i] = j
  }
  b[0..n]
end
p b(9, n) # Seiichi Manyama, May 04 2016

Crossrefs

Cf. A006721, A078495, A268199, A271954, A271948, A271949, A271950, A271952, A271955.

Sequence in context: A017904 A368902 A143290 * A044961 A044823 A048309

Adjacent sequences: A272035 A272036 A272037 * A272039 A272040 A272041

Keyword

nonn

Author

Vladimir Shevelev and Peter J. C. Moses, Apr 18 2016

Status

approved