OFFSET
1,4
COMMENTS
a(n+1) is the number of compositions n=p(1)+p(2)+...+p(m) with p(1)=1 and p(k) <= 6*p(k+1). - Joerg Arndt, Dec 18 2012
LINKS
Alois P. Heinz, Table of n, a(n) for n = 1..1000
Christian Elsholtz, Clemens Heuberger, Helmut Prodinger, The number of Huffman codes, compact trees, and sums of unit fractions, arXiv:1108.5964v1 [math.CO], Aug 30, 2011. Also IEEE Trans. Information Theory, Vol. 59, No. 2, 2013 pp. 1065-1075.
FORMULA
a(n) = A294775(n-1,5). - Alois P. Heinz, Nov 08 2017
MATHEMATICA
b[n_, r_, k_] := b[n, r, k] = If[n < r, 0, If[r == 0, If[n == 0, 1, 0], Sum[b[n - j, k (r - j), k], {j, 0, Min[n, r]}]]];
a[n_] := b[5n-4, 1, 6];
Array[a, 40] (* Jean-François Alcover, Jul 21 2018, after Alois P. Heinz *)
PROG
(PARI) /* see A002572, set t=6 */
CROSSREFS
KEYWORD
nonn
AUTHOR
Jonathan Vos Post, Aug 30 2011
EXTENSIONS
Terms beyond a(20)=122910 added by Joerg Arndt, Dec 18 2012
Invalid empirical g.f. removed by Alois P. Heinz, Nov 08 2017
STATUS
approved