OFFSET
1,2
COMMENTS
Row sums = A143128. - Gary W. Adamson, Jul 26 2008
LINKS
Indranil Ghosh, Rows 1..100, flattened
FORMULA
EXAMPLE
T(4,2)=14 because the divisors of 2 are {1,2}, the divisors of 3 are {1,3} and the divisors of 4 are {1,2,4}; sum of all these divisors is 14.
Triangle begins:
1;
4, 3;
8, 7, 4;
15, 14, 11, 7;
21, 20, 17, 13, 6;
...
MAPLE
with(numtheory): T:=(n, k)->add(sigma(j), j=k..n): for n from 1 to 12 do seq(T(n, k), k=1..n) od; # yields sequence in triangular form
MATHEMATICA
T[n_, n_] := DivisorSigma[1, n]; T[n_, k_] := Sum[DivisorSigma[1, j], {j, k, n}]; Table[T[n, k], {n, 1, 10}, {k, 1, n}] // Flatten (* G. C. Greubel, Sep 03 2017 *)
CROSSREFS
KEYWORD
nonn,tabl
AUTHOR
Emeric Deutsch, Aug 02 2005
STATUS
approved