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A322122
Number of positive integers that are not the sum of 3 squares and a nonnegative (2n + 1)-st power.
1
0, 0, 17, 191, 1816, 16541, 149320, 1344880, 12106148, 108960347, 980654368, 8825914594, 79433288194, 714899721602, 6434097782077, 57906880685893, 521161927629204, 4690457351939133, 42214116174823814, 379927045590000351, 3419343410347321718
OFFSET
1,3
FORMULA
a(n) = Sum_{k=2..n-1} (floor(3^(2n+1)/2^(2k+3)-7/8) + 1).
MATHEMATICA
a[n_]:=Sum[Floor[3^(2n+1)/2^(2k+3)-7/8]+1, {k, 2, n-1}];
Table[a[n], {n, 21}]
CROSSREFS
KEYWORD
nonn
AUTHOR
XU Pingya, Nov 27 2018
STATUS
approved