login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 59th year, we have over 358,000 sequences, and we’ve crossed 10,300 citations (which often say “discovered thanks to the OEIS”).

Other ways to Give
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A061796 Number of distinct sums sigma(i) + sigma(j) for 1<=i<=j<=n, where sigma(k) = A000203(k). 0

%I

%S 1,3,6,9,12,17,18,23,27,30,30,39,40,45,45,51,51,60,60,66,69,72,72,81,

%T 81,81,86,92,94,103,103,112,112,114,114,131,133,133,133,141,141,151,

%U 153,155,157,157,157,175,178,185,185,193,193,202,202,202,205,205,205

%N Number of distinct sums sigma(i) + sigma(j) for 1<=i<=j<=n, where sigma(k) = A000203(k).

%e 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 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.

%t f[x_] := DivisorSigma[1, x] t0=Table[Length[Union[Flatten[Table[f[u]+f[w], {w, 1, m}, {u, 1, m}]]]], {m, 1, 75}]

%Y Cf. A000217, A000203.

%K nonn

%O 1,2

%A _Labos Elemer_, Jun 22 2001

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified December 7 07:00 EST 2022. Contains 358649 sequences. (Running on oeis4.)