OFFSET
2,4
LINKS
Michael De Vlieger, Table of n, a(n) for n = 2..10000
FORMULA
Shifts left under transform T where Ta has Dirichlet g.f.: 1/(1-A(s)).
EXAMPLE
The different ways of writing the numbers 2 through 7 as lterms are:
2 = 2,
3 = 1 + 2,
4 = 1 + (1+2),
5 = 1 + (1+1+2) = 1 + 2*2,
6 = 1 + (1+1+1+2) = 1 + (1+2*2),
7 = 1 + (1+1+1+1+2) = 1 + (1+1+2*2) = 1 + 2*(1+2) = 1 + (1+2)*2.
MATHEMATICA
Fold[Function[{a, n}, Append[a, DivisorSum[n, a[[#]] a[[n/# - 1]] &, # < n &]]], {1}, Range[2, 53]] (* Michael De Vlieger, Mar 14 2018 *)
PROG
(PARI) a(n)=if(n<2, 1, sumdiv(n, d, if(d<n, a(d)*a(n/d-1), 0))) \\ Benoit Cloitre, Mar 13 2018
CROSSREFS
KEYWORD
nonn,eigen
AUTHOR
Christian G. Bower, Oct 15 1999
STATUS
approved