A294303 Sum of the eighth powers of the parts in the partitions of n into two distinct parts.
0, 0, 257, 6562, 72354, 456418, 2142595, 7841860, 24684612, 67340708, 167731333, 380410598, 812071910, 1622037830, 3103591687, 5649705096, 9961449608, 16894160328, 27957167625, 44840730666, 70540730666, 108149231146, 163239463563, 241120467148, 351625763020
Offset: 1
Links
- David A. Corneth, Table of n, a(n) for n = 1..10000
- Index entries for sequences related to partitions
- Index entries for linear recurrences with constant coefficients, signature (1,9,-9,-36,36,84,-84,-126,126,126,-126,-84,84,36,-36,-9,9,1,-1).
Programs
-
Mathematica
Table[Sum[i^8 + (n - i)^8, {i, Floor[(n-1)/2]}], {n, 30}] -
PARI
first(n) = {my(res = vector(n, i, 1/9*i^9 - 1/2*i^8 + 2/3*i^7 - 7/15*i^5 + 2/9*i^3 - 1/30*i)); forstep(i = 2, #res, 2, res[i] -= i^8/256); res} \\ David A. Corneth, Nov 05 2017 -
PARI
concat(vector(2), Vec(x^3*(257 + 6305*x + 63479*x^2 + 327319*x^3 + 1103301*x^4 + 2469669*x^5 + 4014083*x^6 + 4659395*x^7 + 4014083*x^8 + 2480995*x^9 + 1103301*x^10 + 331365*x^11 + 63479*x^12 + 6551*x^13 + 257*x^14 + x^15) / ((1 - x)^10*(1 + x)^9) + O(x^40))) \\ Colin Barker, Nov 20 2017
Formula
a(n) = Sum_{i=1..floor((n-1)/2)} i^8 + (n-i)^8.
From David A. Corneth, Nov 05 2017: (Start)
For odd n, a(n) = n^9 / 9 - n^8/2 + 2*n^7 / 3 - 7*n^5 / 15 + 2*n^3 / 9 - n/30
For even n, a(n) = n^9 / 9 - 129*n^8/256 + 2*n^7 / 3 - 7*n^5 / 15 + 2*n^3 / 9 - n/30.
(End)
From Colin Barker, Nov 20 2017: (Start)
G.f.: x^3*(257 + 6305*x + 63479*x^2 + 327319*x^3 + 1103301*x^4 + 2469669*x^5 + 4014083*x^6 + 4659395*x^7 + 4014083*x^8 + 2480995*x^9 + 1103301*x^10 + 331365*x^11 + 63479*x^12 + 6551*x^13 + 257*x^14 + x^15) / ((1 - x)^10*(1 + x)^9).
a(n) = a(n-1) + 9*a(n-2) - 9*a(n-3) - 36*a(n-4) + 36*a(n-5) + 84*a(n-6) - 84*a(n-7) - 126*a(n-8) + 126*a(n-9) + 126*a(n-10) - 126*a(n-11) - 84*a(n-12) + 84*a(n-13) + 36*a(n-14) - 36*a(n-15) - 9*a(n-16) + 9*a(n-17) + a(n-18) - a(n-19) for n>19.
(End)