This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A109976 Diagonal sums of number triangle A109974. 2
 1, 2, 3, 6, 7, 16, 19, 46, 66, 159, 274, 667, 1320, 3263, 7156, 18084, 42794, 111018, 278752, 743889, 1959482, 5383395, 14761634, 41740307, 118517301, 344580865, 1009349749, 3013665637, 9081346743, 27808754039, 86015003997, 269796018547 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Robert Israel, Table of n, a(n) for n = 0..1063 FORMULA a(n) = Sum_{k=0..floor(n/2)} sigma_k(n-2k+1). - Corrected by Robert Israel, May 25 2018 G.f.: Sum_{n>=1} x^(n-1)/((1-x^n)*(1-n*x^2)). - Robert Israel, May 27 2018 MAPLE f:= n -> add(numtheory:-sigma[k](n-2*k+1), k=0..n/2): map(f, [\$0..50]); # Robert Israel, May 25 2018 MATHEMATICA Array[Sum[DivisorSigma[k, (# - 2 k + 1)], {k, 0, Floor[#/2]}] &, 32, 0] (* Michael De Vlieger, May 27 2018 *) CROSSREFS Cf. A109974 Sequence in context: A137604 A034901 A275390 * A011768 A052487 A067951 Adjacent sequences:  A109973 A109974 A109975 * A109977 A109978 A109979 KEYWORD easy,nonn AUTHOR Paul Barry, Jul 06 2005 STATUS approved

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

Last modified October 16 11:23 EDT 2019. Contains 328056 sequences. (Running on oeis4.)