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A152864 Deficiency of n, plus the number of proper divisors of n: a(n) = 2n - sigma(n) + d(n) - 1. 4
1, 2, 3, 3, 5, 3, 7, 4, 7, 5, 11, 1, 13, 7, 9, 5, 17, 2, 19, 3, 13, 11, 23, -5, 21, 13, 17, 5, 29, -5, 31, 6, 21, 17, 25, -11, 37, 19, 25, -3, 41, -5, 43, 9, 17, 23, 47, -19, 43, 12, 33, 11, 53, -5, 41, -1, 37, 29, 59, -37, 61, 31 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
FORMULA
a(n) = A005843(n)-A000203(n)+A000005(n)-1 = A033879(n)+A032741(n).
MATHEMATICA
a[n_] := 2*n - Differences[DivisorSigma[{0, 1}, n]][[1]] - 1; Array[a, 100] (* Amiram Eldar, Apr 07 2024 *)
PROG
(PARI) a(n) = 2*n - sigma(n) + numdiv(n) - 1; \\ Amiram Eldar, Apr 07 2024
CROSSREFS
Sequence in context: A105555 A066858 A333496 * A152984 A177980 A215405
KEYWORD
easy,sign
AUTHOR
Omar E. Pol, Dec 14 2008
STATUS
approved

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Last modified May 29 05:22 EDT 2024. Contains 372921 sequences. (Running on oeis4.)