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A294930
Characteristic function for A091191, primitive abundant numbers: abundant numbers (A005101) having no abundant proper divisor.
7
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0
OFFSET
1
FORMULA
a(n) = A294937(n) * [0==A294929(n)].
a(n) = 1 iff A080224(n) = 1.
MATHEMATICA
a[n_] := Boole[Count[Divisors[n], _?(DivisorSigma[1, #] > 2*# &)] == 1]; Array[a, 100] (* Amiram Eldar, Mar 18 2024 *)
PROG
(PARI)
A294937(n) = (sigma(n)>(2*n));
A294929(n) = sumdiv(n, d, (d<n)*A294937(d));
A294930(n) = (A294937(n)*(0==A294929(n)));
KEYWORD
nonn
AUTHOR
Antti Karttunen, Nov 14 2017
STATUS
approved