A075670 Sum of next n 9th powers.

1, 20195, 12292965, 1561991824, 77226633575, 2014634387961, 33098483802475, 383318212734080, 3377498614484589, 23898971839102975, 141290020118952881, 719054471032657200, 3223613105991831475, 12964037775857022869

Offset

1,2

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..10000

Formula

a(1)=1; a(n)=sum(i^s, {i, n(n-1)/2+1, n(n-1)/2+1+n}).

a(n) = (5n^19 + 105n^17 + 666n^15 + 1530n^13 + 689n^11 - 995n^9 + 304n^7 + 640n^5 - 384n^3)/2560.

G.f.: x*(x^18 +20175*x^17 +11889255*x^16 +1319968434*x^15 +48299442990*x^14 +752964012192*x^13 +5757432094050*x^12 +23468751060270*x^11 +53583908362248*x^10 +70362713036770*x^9 +53583908362248*x^8 +23468751060270*x^7 +5757432094050*x^6+752964012192*x^5 +48299442990*x^4 +1319968434*x^3 +11889255*x^2 +20175*x +1)/(x -1)^20. [Colin Barker, Sep 06 2012]

Example

s=9; a(1) = 1^s = 1; a(2) = 2^s + 3^s = 2^9 + 3^9 = 20195; a(3) = 4^s + 5^s + 6^s = 12292965, a(4) = 7^s + 8^s + 9^s + 10^3 = 1561991824.

Mathematica

i1 := n(n-1)/2+1; i2 := n(n-1)/2+n; s=9; Table[Sum[i^s, {i, i1, i2}], {n, 20}]
Total[#^9]&/@(Range[First[#]+1, Last[#]]&/@Partition[Accumulate[Range[ 0, 15]], 2, 1]) (* Harvey P. Dale, Oct 05 2011 *)

Prog

(Magma) [(5*n^19 + 105*n^17 + 666*n^15 + 1530*n^13 + 689*n^11 - 995*n^9 + 304*n^7 + 640*n^5 - 384*n^3)/2560 : n in [1..20]]; // Vincenzo Librandi, Oct 06 2011

Crossrefs

Cf. A072474 (s=2), A075664 - A075670 (s=3-10), A075671 (s=n).

Cf. A006003, A072474, A075664 - A075671.

Sequence in context: A031682 A052358 A052189 * A053073 A295014 A133527

Adjacent sequences: A075667 A075668 A075669 * A075671 A075672 A075673

Keyword

nonn,easy

Author

Zak Seidov, Sep 24 2002

Extensions

Formula from Charles R Greathouse IV, Sep 17 2009

Status

approved