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A161886
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Number of nonzero elements in the n X n Redheffer matrix.
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6
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1, 4, 7, 11, 14, 19, 22, 27, 31, 36, 39, 46, 49, 54, 59, 65, 68, 75, 78, 85, 90, 95, 98, 107, 111, 116, 121, 128, 131, 140, 143, 150, 155, 160, 165, 175, 178, 183, 188, 197, 200, 209, 212, 219, 226, 231, 234, 245, 249, 256, 261, 268, 271, 280, 285, 294, 299, 304
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OFFSET
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1,2
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LINKS
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FORMULA
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EXAMPLE
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The 4x4 Redheffer matrix:
1,1,1,1
1,1,0,0
1,0,1,0
1,1,0,1
contains 11 nonzero elements.
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MATHEMATICA
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PROG
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(Python)
from math import isqrt
def A161886(n): return (lambda m: 2*sum(n//k for k in range(1, m+1))+n-1-m*m)(isqrt(n)) # Chai Wah Wu, Oct 09 2021
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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