|
|
A061795
|
|
Number of distinct sums phi(i) + phi(j) for 1 <= i <= j <= n, phi(k) = A000010(k).
|
|
1
|
|
|
1, 1, 3, 3, 6, 6, 9, 9, 9, 9, 13, 13, 17, 17, 18, 18, 22, 22, 26, 26, 26, 26, 30, 30, 32, 32, 32, 32, 37, 37, 41, 41, 41, 41, 43, 43, 47, 47, 47, 47, 53, 53, 57, 57, 57, 57, 62, 62, 62, 62, 63, 63, 67, 67, 67, 67, 67, 67, 72, 72, 79, 79, 79, 79, 81, 81, 86, 86, 87, 87, 93, 93
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,3
|
|
LINKS
|
|
|
EXAMPLE
|
If the {s+t} sums are generated by adding 2 terms of an S set consisting of n different entries, then at least 1, at most n(n+1)/2 = A000217(n) distinct values can be obtained. The set of first n phi-values gives results falling between these two extremes. E.g., n=10, A000010: {1,1,2,2,4,2,6,4,6,4,...}. Additions provide {2,3,4,5,6,7,8,10,12}, i.e., 9 different results. Thus a(10)=9.
|
|
MATHEMATICA
|
f[x_] := EulerPhi[x]; t0=Table[Length[Union[Flatten[Table[f[u]+f[w], {w, 1, m}, {u, 1, m}]]]], {m, 1, 75}]
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|