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A299796 Largest number k that is not the sum of 3 squares and a nonnegative (2n+5)-th power. 3
2160, 19568, 177136, 1594304, 14348784, 129140160, 1162261440, 10460353136, 94143178736, 847288609392, 7625597484912, 68630377364848, 617673396283888, 5559060566555504, 50031545098999664, 450283905890997360, 4052555153018976240, 36472996377170786288 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Subsequence of A004215.

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

FORMULA

a(n) = max_{2<=i<=n+1, j>=0} {4^i*(8j+7) : 4^i*(8j+7) < 3^(2n+5)}.

EXAMPLE

2160 is not the sum of 3 squares and a nonnegative 7th power, and all integers larger than 2160 can be represented as the sum of 3 squares and a nonnegative 7th power (see A297970). Thus a(1) = 2160.

MATHEMATICA

a[n_]:= Max@Table[4^k (8 Floor[3^(2 n + 5) / 2^(2 k + 3) - 7 / 8] + 7), {k, 2, n + 1}] Table[a[n], {n, 18}] (* XU Pingya, Nov 30 2018 *)

CROSSREFS

Cf. A004215, A022552, A297970.

Sequence in context: A179698 A075702 A205629 * A253715 A205331 A154822

Adjacent sequences: A299793 A299794 A299795 * A299797 A299798 A299799

KEYWORD

nonn

AUTHOR

XU Pingya, Feb 19 2018

STATUS

approved

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Last modified January 29 23:01 EST 2023. Contains 359939 sequences. (Running on oeis4.)