A322122 Number of positive integers that are not the sum of 3 squares and a nonnegative (2n + 1)-st power.

0, 0, 17, 191, 1816, 16541, 149320, 1344880, 12106148, 108960347, 980654368, 8825914594, 79433288194, 714899721602, 6434097782077, 57906880685893, 521161927629204, 4690457351939133, 42214116174823814, 379927045590000351, 3419343410347321718

Offset

1,3

Links

Table of n, a(n) for n=1..21.

Wikipedia, Legendre's three-square theorem

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

Cf. A004215, A297788, A273915, A297970, A296579, A299796.

Sequence in context: A021754 A141993 A025467 * A210340 A021494 A300172

Adjacent sequences: A322119 A322120 A322121 * A322123 A322124 A322125

Keyword

nonn

Author

XU Pingya, Nov 27 2018

Status

approved