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A105086
Sum of the divisors of n minus the least nontrivial proper divisor of n.
2
1, 1, 5, 1, 10, 1, 13, 10, 16, 1, 26, 1, 22, 21, 29, 1, 37, 1, 40, 29, 34, 1, 58, 26, 40, 37, 54, 1, 70, 1, 61, 45, 52, 43, 89, 1, 58, 53, 88, 1, 94, 1, 82, 75, 70, 1, 122, 50, 91, 69, 96, 1, 118, 67, 118, 77, 88, 1, 166, 1, 94, 101, 125, 79, 142, 1, 124, 93, 142, 1, 193, 1, 112
OFFSET
2,3
COMMENTS
a(n) = 1 iff n is prime.
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 2..10000
FORMULA
a(n) = sigma(n) - least nontrivial proper divisor(n).
a(n) = A000203(n) - A020639(n), n >= 2. - Omar E. Pol, Dec 08 2019
EXAMPLE
a(6) = 10 because sigma(6) = 1 + 2 + 3 + 6 = 12, least nontrivial proper divisor(6) = 2 and their difference is 10.
MATHEMATICA
a[n_] := DivisorSigma[1, n] - Divisors[n][[2]]
PROG
(PARI) a(n)=sigma(n) - divisors(n)[2] \\ Charles R Greathouse IV, Dec 10 2019
CROSSREFS
Sequence in context: A146070 A308504 A040029 * A305838 A329373 A147362
KEYWORD
nonn
AUTHOR
Toby Donaldson (tjd(AT)sfu.ca), Apr 07 2005
EXTENSIONS
Edited and extended by Robert G. Wilson v, Apr 08 2005
Offset changed by Charles R Greathouse IV, Dec 10 2019
STATUS
approved