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A001209 a(n) is the solution to the postage stamp problem with 4 denominations and n stamps.

%I A001209 M3432 N1568 #48 Feb 16 2025 08:32:22
%S A001209 4,12,24,44,71,114,165,234,326,427,547,708,873,1094,1383,1650,1935,
%T A001209 2304,2782,3324,3812,4368,5130,5892,6745,7880,8913,9919,11081,12376,
%U A001209 13932,15657,17242,18892,21061,23445,25553,27978,31347,33981,36806,39914,43592
%N A001209 a(n) is the solution to the postage stamp problem with 4 denominations and n stamps.
%C A001209 _Fred Lunnon_ [W. F. Lunnon] defines "solution" to be the smallest value not obtainable by the best set of stamps. The solutions given are one lower than this, that is, the sequence gives the largest number obtainable without a break using the best set of stamps.
%C A001209 Challis lists up to a(54) and provides recursions up to a(157). - _R. J. Mathar_, Apr 01 2006
%C A001209 Additional terms a(29) through a(254) can be computed using 3 sets of equations and a table of 10 coefficients available on line at Challis and Robinson. - John P Robinson (john-robinson(AT)uiowa.edu), Feb 18 2010
%D A001209 R. K. Guy, Unsolved Problems in Number Theory, C12.
%D A001209 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
%D A001209 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H A001209 Robert Price, <a href="/A001209/b001209.txt">Table of n, a(n) for n = 1..54</a>
%H A001209 R. Alter and J. A. Barnett, <a href="http://www.jstor.org/stable/2321610">A postage stamp problem</a>, Amer. Math. Monthly, 87 (1980), 206-210.
%H A001209 M. F. Challis, <a href="http://dx.doi.org/10.1093/comjnl/36.2.117">Two new techniques for computing extremal h-bases A_k</a>, Comp. J. 36(2) (1993) 117-126
%H A001209 M. F. Challis and J. P. Robinson, <a href="http://www.cs.uwaterloo.ca/journals/JIS/VOL13/Challis/challis6.html">Some Extremal Postage Stamp Bases</a>, J. Integer Seq., 13 (2010), Article 10.2.3.
%H A001209 Erich Friedman, <a href="https://erich-friedman.github.io/mathmagic/0403.html">Postage stamp problem</a>
%H A001209 W. F. Lunnon, <a href="https://doi.org/10.1093/comjnl/12.4.377">A postage stamp problem</a>, Comput. J. 12 (1969) 377-380.
%H A001209 S. Mossige, <a href="https://doi.org/10.1090/S0025-5718-1981-0606515-1">Algorithms for Computing the h-Range of the Postage Stamp Problem</a>, Math. Comp. 36 (1981) 575-582.
%H A001209 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/PostageStampProblem.html">Postage stamp problem</a>
%Y A001209 Postage stamp sequences: A001208, A001209, A001210, A001211, A001212, A001213, A001214, A001215, A001216, A005342, A005343, A005344, A014616, A053346, A053348, A075060, A084192, A084193.
%Y A001209 Equals A196069 - 1.
%Y A001209 A row or column of the array A196416 (possibly with 1 subtracted from it).
%K A001209 nonn
%O A001209 1,1
%A A001209 _N. J. A. Sloane_
%E A001209 Entry improved by comments from John Seldon (johnseldon(AT)onetel.com), Sep 15 2004
%E A001209 a(15) to a(28) from Table 1 of Mossige reference added by _R. J. Mathar_, Mar 29 2006
%E A001209 a(29)-a(54) from Challis and Robinson added by _Robert Price_, Jul 19 2013