A355915 Number of ways to write n as a sum of numbers of the form 2^r * 3^s, where r and s are >= 0, and no summand divides another.
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 2, 1, 1, 1, 1, 1, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 2, 1, 1, 2, 1, 1, 2, 1, 1, 2, 1, 3, 1, 1, 1, 2, 1, 1, 1, 2, 2, 1, 1, 1, 2, 1, 1, 3, 2, 2, 1, 1, 2, 2, 1, 2, 2, 1, 2, 1, 1, 2, 1, 1, 2, 2, 1, 3, 1, 2, 2, 3, 1, 2, 1, 2, 2, 2, 1, 3, 3, 2, 1
Offset: 1
Keywords
Examples
Illustration of initial terms: 1 = 2^0 2 = 2^1 3 = 3^1 4 = 2^2 5 = 2+3 6 = 2*3 7 = 2^2+3 8 = 2^3 9 = 3^2 10 = 2^2 + 2*3 11 = 2+3^2 = 2^3+3 (this is the first time there are 2 solutions) 12 = 2^2*3 13 = 2^2+3^2 14 = 2^3+2*3 ...
Links
- Michael S. Branicky, Table of n, a(n) for n = 1..10000
- Michael S. Branicky, Python Program
- William Lowell Putman Mathematical Competition, Number 66, 2005, Problem A-1.
Programs
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Python
# see linked program
Extensions
More than the usual number of terms are shown, to distinguish this from similar sequences.
Comments