OFFSET
1,2
FORMULA
EXAMPLE
For n = 10, the first ten odd numbers are 1, 3, 5, 7, 9, 11, 13, 15, 17, 19. The last of them is A005408(10-1) = 19. On the other hand the sum of the aliquot parts of 10 is 1 + 2 + 5 = 8, so a(10) = 19 - 8 = 11.
MATHEMATICA
a[n_] := 3*n - 1 - DivisorSigma[1, n]; Array[a, 75] (* Amiram Eldar, May 21 2022 *)
PROG
(PARI) a(n) = 3*n-1-sigma(n); \\ Michel Marcus, May 04 2022
CROSSREFS
KEYWORD
nonn
AUTHOR
Omar E. Pol, Apr 29 2022
STATUS
approved