Faster gamma calculation #1050

Job	Run time
ruby-versions / Generate Ruby versions	5s
ubuntu-latest head	42s
ubuntu-latest 3.1	52s
ubuntu-latest 3.4	52s
ubuntu-latest 4.0	49s
ubuntu-latest 3.3	58s
ubuntu-latest 3.0	53s
ubuntu-latest debug	48s
macos-14 2.7	1m 16s
ubuntu-latest 2.7	1m 23s
macos-latest 2.7	1m 51s
macos-latest 4.0	58s
macos-latest 3.3	38s
ubuntu-latest 3.2	57s
macos-latest 3.0	33s
macos-latest debug	46s
windows-latest 3.4	3m 32s
macos-latest 3.4	1m 13s
macos-latest 3.2	52s
macos-14 4.0	22s
macos-latest 3.1	50s
macos-14 3.1	42s
windows-latest 3.3	3m 30s
macos-14 3.3	29s
windows-latest 4.0	3m 24s
macos-14 3.4	40s
macos-14 3.0	30s
macos-14 3.2	41s
macos-14 head	31s
macos-14 debug	29s
windows-latest head	3m 28s
windows-latest mingw	3m 22s
windows-latest mswin	2m 15s
macos-latest head	41s
windows-latest 2.7	4m 47s
	46m 39s

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