/usr/share/sextractor/block_3x3.conv is in sextractor 2.4.4-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 | CONV NORM
# 3x3 convolution mask of a block-function PSF (ex: DeNIS PSF).
1 1 1
1 1 1
1 1 1
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