|
Search: id:A061796
|
|
|
| A061796 |
|
Number of distinct sums sigma(i) + sigma(j) for 1<=i<=j<=n, where sigma(k) = A000203(k). |
|
+0
1
|
|
| 1, 3, 6, 9, 12, 17, 18, 23, 27, 30, 30, 39, 40, 45, 45, 51, 51, 60, 60, 66, 69, 72, 72, 81, 81, 81, 86, 92, 94, 103, 103, 112, 112, 114, 114, 131, 133, 133, 133, 141, 141, 151, 153, 155, 157, 157, 157, 175, 178, 185, 185, 193, 193, 202, 202, 202, 205, 205, 205
(list; graph; listen)
|
|
|
OFFSET
|
1,2
|
|
|
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 sigma-values gives results falling between these two extremes.
E.g. n=10, A000203: {1,3,4,7,6,12,8,15,13,18...}. The 55 possible sigma(i)+sigma(j) additions give 30 different results: {2,4,5,6,...,33,36}. Therefore a(10)=30.
|
|
MATHEMATICA
|
f[x_] := DivisorSigma[1, x] t0=Table[Length[Union[Flatten[Table[f[u]+f[w], {w, 1, m}, {u, 1, m}]]]], {m, 1, 75}]
|
|
CROSSREFS
|
Cf. A000217, A000203.
Sequence in context: A084525 A130248 A072567 this_sequence A113241 A127621 A049707
Adjacent sequences: A061793 A061794 A061795 this_sequence A061797 A061798 A061799
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
Labos E. (labos(AT)ana.sote.hu), Jun 22 2001
|
|
|
Search completed in 0.002 seconds
|
