The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A138357 Floor of sum of the first n^2 square roots. 0
 0, 1, 6, 19, 44, 85, 146, 231, 345, 490, 671, 892, 1157, 1470, 1836, 2257, 2738, 3283, 3896, 4581, 5343, 6184, 7109, 8122, 9227, 10428, 11730, 13135, 14648, 16273, 18014, 19875, 21861, 23974, 26219, 28600, 31121, 33786, 36600, 39565, 42686, 45967 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS a(n)-A005900(n)={0,0,0,0,0,0,0,1,1,1,1,1,1,2,2,2,2,2,2,3,3,3,3,3,3,4,4,4,4,4,4,5,5,5,5,5,5,6,6,6,...} LINKS MATHEMATICA A[n_]:=Floor[HarmonicNumber[n^2, -1/2]] (* or *) A[n_]:=Floor[(2/3)n^3+n/2+1/(24n)+Zeta[ -1/2]] nn=50; With[{c=Sqrt[Range[nn^2]]}, Table[Floor[Total[Take[c, n^2]]], {n, 0, nn}]] (* Harvey P. Dale, Apr 21 2012 *) PROG (PARI) a(n)=floor(sum(x=0, n^2, sqrt(x))) CROSSREFS Cf. A005900 (Octahedral numbers:(2n^3+n)/3). Sequence in context: A035495 A061293 A005900 * A299264 A183763 A209403 Adjacent sequences:  A138354 A138355 A138356 * A138358 A138359 A138360 KEYWORD nonn AUTHOR Zak Seidov, Mar 16 2008 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 April 20 23:46 EDT 2021. Contains 343143 sequences. (Running on oeis4.)