A167809 Number of admissible bases in the postage stamp problem for n denominations and h = 2 stamps.

1, 2, 5, 17, 65, 292, 1434, 7875, 47098, 305226, 2122983, 15752080, 124015310, 1031857395, 9041908204, 83186138212, 801235247145, 8059220936672, 84463182889321

Offset

1,2

Comments

A basis 1 = b_1 < b_2 ... < b_n is admissible if all the values 1 <= x <= b_n are obtainable as a sum of at most h (not necessarily distinct) numbers in the basis.

Conjecture: a(n) >= A000108(n). - Michael Chu, May 16 2022

References

R. K. Guy, Unsolved Problems in Number Theory, C12.

Links

Table of n, a(n) for n=1..19.

R. Alter and J. A. Barnett, A postage stamp problem, Amer. Math. Monthly, 87 (1980), 206-210.

M. F. Challis, Two new techniques for computing extremal h-bases A_k, Comp J 36(2) (1993) 117-126

Erich Friedman, Postage stamp problem

J. Kohonen, A meet-in-the-middle algorithm for finding extremal restricted additive 2-bases, arXiv preprint arXiv:1403.5945 [math.NT], 2014 and J. Int. Seq. 17 (2014) # 14.6.8.

J. Kohonen, Early Pruning in the Restricted Postage Stamp Problem, arXiv preprint arXiv:1503.03416 [math.NT], 2015.

W. F. Lunnon, A postage stamp problem, Comput. J. 12 (1969) 377-380.

S. Mossige, Algorithms for Computing the h-Range of the Postage Stamp Problem, Math. Comp. 36 (1981) 575-582.

Crossrefs

Other enumerations with different parameters: A167809 (h = 2), A167810 (h = 3), A167811 (h = 4), A167812 (h = 5), A167813 (h = 6), A167814 (h = 7).

For h = 2, cf. A008932.

Sequence in context: A052539 A123166 A008932 * A262449 A346506 A362967

Adjacent sequences: A167806 A167807 A167808 * A167810 A167811 A167812

Keyword

hard,more,nonn

Author

Yogy Namara (yogy.namara(AT)gmail.com), Nov 12 2009

Extensions

a(17) from simple depth-first search by Jukka Kohonen, Jun 16 2016

a(18)-a(19) from depth-first search by Jukka Kohonen, Jul 30 2016

Status

approved