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%I #21 Apr 05 2020 05:06:26
%S 1,1,2,3,5,9,13,23,36,65,100,175,275,468,760,1266,2077,3454,5690,9449,
%T 15547,25709,42459,70181,115947,191509,316570,523087,864406,1428174,
%U 2359266
%N a(n) is the number of numbers m such that the number of iterations of r -> r - (largest divisor d < r) needed to reach 1 starting at r = m is equal to n.
%e Example (a(4)=5): There are five numbers (7,9,10,12,16) with 4 steps of defined iteration: 7-1=6, 6-3=3, 3-1=2, 2-1=1; 9-3=6, 6-3=3, 3-1=2, 2-1=1; 10-5=5, 5-1=4, 4-2=2, 2-1=1; 12-6=6, 6-3=3, 3-1=2, 2-1=1; 16-8=8, 8-4=4, 4-2=2, 2-1=1.
%o (PARI) a064097(n)={my(k=1,d=divisors(n),r=n-d[#d-1]);while(r>1,d=divisors(r);r-=d[#d-1];k++);k};
%o my(c=vector(50));for(k=2,2^20,j=a064097(k);c[j]++);concat([1],c[1..20]) \\ _Hugo Pfoertner_, Mar 23 2020
%Y Cf. A000079, A064097, A105017.
%K nonn,more
%O 0,3
%A _Jaroslav Krizek_, Feb 15 2010
%E a(8)-a(27) from _Hugo Pfoertner_, Mar 23 2020
%E a(28)-a(30) from _Robert G. Wilson v_, Apr 05 2020
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