A361507 a(0) = 1; thereafter a(n) = floor((9/4)*a(n-1)) + 1.

1, 3, 7, 16, 37, 84, 190, 428, 964, 2170, 4883, 10987, 24721, 55623, 125152, 281593, 633585, 1425567, 3207526, 7216934, 16238102, 36535730, 82205393, 184962135, 416164804, 936370810, 2106834323, 4740377227, 10665848761, 23998159713, 53995859355, 121490683549, 273354037986, 615046585469, 1383854817306, 3113673338939

Offset: 0

Author

N. J. A. Sloane, Mar 20 2023, following a suggestion from Don Knuth

Keywords

• nonn

References

• N. Tokuda, An efficient Shell's method of sorting by generalized scheme, Department of Computer Science, Utunomiya University, 1989; 10 pages plus 9 unnumbered pages of tables and charts.

Links

• Paolo Xausa, Table of n, a(n) for n = 0..1000

Crossrefs

Other sequences used for Shell sort: A003462, A033622, A036562, A036564, A036569, A055875, A055876, A108870, A361506.

Programs

Mathematica

NestList[Floor[9/4#]+1&,1,50] (* Paolo Xausa, Dec 02 2023 *)