OFFSET
1,5
COMMENTS
In general, a(3n-1) is larger than a(3n-2) and a(3n), which explains the bimodal nature of the graph. - T. D. Noe, Jan 29 2007
REFERENCES
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
M. L. Stein and P. R. Stein, Tables of the Number of Binary Decompositions of All Even Numbers Less Than 200,000 into Prime Numbers and Lucky Numbers. Report LA-3106, Los Alamos Scientific Laboratory of the University of California, Los Alamos, NM, Sep 1964.
LINKS
T. D. Noe, Table of n, a(n) for n = 1..10000
V. Gardiner, R.Lazarus, N. Metropolis and S. Ulam, On certain sequences of integers defined by sieves, Math. Mag., 29 (1955), 117-119.
MATHEMATICA
nmax = 1000;
luckies = Table[2i+1, {i, 0, nmax}]; For[n = 2, n < Length[luckies], r = luckies[[n++]]; luckies = ReplacePart[luckies, Table[r*i -> Nothing, {i, 1, Length[luckies]/r}]]];
a[n_] := IntegerPartitions[2n, {2}, luckies] // Length;
CROSSREFS
KEYWORD
nonn,easy,nice
AUTHOR
EXTENSIONS
Paul Zimmermann points out that the second term was incorrectly given as 2 in the Encyclopedia of Integer Sequences.
Missing a(71)-a(73) inserted by Sean A. Irvine, Nov 05 2014
STATUS
approved