login
A330872
Numbers k such that k and k+1 are both primitive abundant numbers (A071395).
7
82004, 158235, 516704, 2921535, 5801984, 10846016, 12374144, 12603824, 18738224, 24252074, 32409530, 33696975, 35356544, 36149295, 41078114, 42541190, 43485584, 65090864, 88304475, 90725775, 181480695, 183872535, 213261795, 233762528, 242301344, 254502495, 254630144
OFFSET
1,1
COMMENTS
Not to be confused with A283418 in which the primitive abundant numbers can have perfect numbers as divisors (as defined in A091191).
LINKS
EXAMPLE
82004 is a term since both 82004 and 82005 are abundant, and all of their proper divisors are deficient numbers.
MATHEMATICA
primAbQ[n_] := DivisorSigma[1, n] > 2 n && AllTrue[Most @ Rest @ Divisors[n], DivisorSigma[1, #] < 2*# &]; q1 = False; seq = {}; Do[q2 = primAbQ[n]; If[q1 && q2, AppendTo[seq, n - 1]]; q1 = q2, {n, 2, 6*10^6}]; seq
CROSSREFS
Subsequence of A005101, A071395, A096399 and A283418.
Sequence in context: A146025 A361934 A283418 * A253957 A253964 A253760
KEYWORD
nonn
AUTHOR
Amiram Eldar, Apr 29 2020
STATUS
approved