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A371388
a(n) = 2*n*floor(n*(1 + sqrt(5))/2) - n^2. Main diagonal of A340429.
2
1, 8, 15, 32, 55, 72, 105, 128, 171, 220, 253, 312, 377, 420, 495, 544, 629, 720, 779, 880, 945, 1056, 1173, 1248, 1375, 1508, 1593, 1736, 1827, 1980, 2139, 2240, 2409, 2584, 2695, 2880, 2997, 3192, 3393, 3520, 3731, 3864, 4085, 4312, 4455, 4692, 4935, 5088, 5341
OFFSET
1,2
FORMULA
a(n) = 2*n*A000201(n) - n^2.
MATHEMATICA
Array[2 * # * Floor[# * GoldenRatio] - #^2 &, 100]
PROG
(Python)
from math import isqrt
def A371388(n): return n*((n+isqrt(5*n**2)&-2)-n) # Chai Wah Wu, Mar 21 2024
CROSSREFS
Cf. A340429.
Sequence in context: A123526 A083686 A293360 * A287644 A089954 A134020
KEYWORD
nonn,easy
AUTHOR
Paolo Xausa, Mar 21 2024
STATUS
approved