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A309759 Numbers that are sums of consecutive powers of 4. 4
1, 4, 5, 16, 20, 21, 64, 80, 84, 85, 256, 320, 336, 340, 341, 1024, 1280, 1344, 1360, 1364, 1365, 4096, 5120, 5376, 5440, 5456, 5460, 5461, 16384, 20480, 21504, 21760, 21824, 21840, 21844, 21845, 65536, 81920, 86016, 87040, 87296, 87360, 87376, 87380 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
Numbers of the form (4^i - 4^j)/3 with i > j.
LINKS
EXAMPLE
336 = 4^2 + 4^3 + 4^4, so 336 is in the sequence.
+------+--------+
| a(n) | base 4*|
+------+--------+
| 1 | 1 |
| 4 | 10 |
| 5 | 11 |
| 16 | 100 |
| 20 | 110 |
| 21 | 111 |
| 64 | 1000 |
| 80 | 1100 |
| 84 | 1110 |
| 85 | 1111 |
+------+--------+
* - a(n) written in base 4.
MATHEMATICA
Module[{nn=10, k}, k=4^Range[0, nn]; Table[Accumulate[Reverse[Take[k, n]]], {n, nn}]]//Flatten (* Harvey P. Dale, May 29 2021 *)
CROSSREFS
Sequence in context: A081345 A137527 A024854 * A025617 A227855 A078581
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Aug 15 2019
STATUS
approved

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Last modified July 18 00:08 EDT 2024. Contains 374377 sequences. (Running on oeis4.)