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A353011
Indices of "late birds" in A090395 (denominator of d(n)/n): indices n such that A090395(k) > A090395(n) for all k > n.
2
2, 12, 24, 36, 60, 72, 84, 96, 108, 180, 240, 252, 360, 480, 504, 720, 792, 1260, 1440, 1680, 1800, 2160, 2340, 2640, 3360, 3600, 5040, 5280, 6720, 7920, 10080, 12600, 15120, 15840, 18480, 20160, 21840, 25200, 30240, 36960, 40320, 43680, 55440, 60480, 65520
OFFSET
1,1
COMMENTS
A090395(n) is the denominator of d(n)/n, where d = A000005 is the number of divisors.
The present sequence gives the indices of those terms of A090395 such that all subsequent terms are larger. This can be used to verify whether a number N is in A091896, which lists the numbers that don't occur in A090395.
It appears that a(n) is divisible by 12 for all n >= 2, by 5 for all n >= 18, by 24 (thus by 120) for all n > 23. Can somebody prove this?
FORMULA
a(n+1) > a(n).
PROG
(PARI) L=List(); forstep(n=m=65520, 1, -1, m>(m=min(A090395(n), m)) && listput(L, n)); Vecrev(L)
CROSSREFS
Cf. A000005 (number of divisors), A090395 (denominator of A000005(n)/n), A091895 (index of first occurrence of n in A090395), A091896 (numbers that don't occur in A090395).
Sequence in context: A269841 A144551 A174457 * A110821 A262983 A356078
KEYWORD
nonn
AUTHOR
M. F. Hasler, Apr 15 2022
STATUS
approved