A362062 - OEIS

%I #17 Apr 07 2023 10:51:45

%S 1,3,10,52,398,4734,78428,1326821,26386288,645482585

%N First index in A362061 where A001221(A362061(a(n))) = n.

%o (Python)

%o from sympy import primefactors

%o from collections import Counter

%o from itertools import count, islice

%o def agen(): # generator of terms

%o     an, c, d, d2, k = 1, Counter(), dict(), dict(), 0

%o     for n in count(1):

%o         if an in d: dpf = d[an]

%o         else: dpf, d2[dpf] = len(primefactors(an)), n

%o         c[dpf] += 1

%o         an = c[dpf]

%o         if k in d2: yield d2[k]; k += 1

%o print(list(islice(agen(), 7))) # _Michael S. Branicky_, Apr 06 2023

%o (Python)

%o from itertools import count

%o from sympy import primenu

%o def A362062(n):

%o     a, b, c = {}, {}, 1

%o     for m in count(1):

%o         d = b[c] = b.get(c,primenu(c))

%o         if d == n: return m

%o         c = a[d] = a.get(d,0)+1 # _Chai Wah Wu_, Apr 07 2023

%Y Cf. A362061, A001221.

%K nonn,more

%O 0,2

%A _Scott R. Shannon_, Apr 06 2023

%E a(9) from _Chai Wah Wu_, Apr 07 2023