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A171405
Sum of divisors of n, excluding divisors 2 and 3.
1
1, 1, 1, 5, 6, 7, 8, 13, 10, 16, 12, 23, 14, 22, 21, 29, 18, 34, 20, 40, 29, 34, 24, 55, 31, 40, 37, 54, 30, 67, 32, 61, 45, 52, 48, 86, 38, 58, 53, 88, 42, 91, 44, 82, 75, 70, 48, 119, 57, 91, 69, 96, 54, 115, 72, 118, 77, 88, 60, 163, 62, 94, 101, 125, 84, 139, 68, 124, 93, 142
OFFSET
1,4
FORMULA
a(n) = A000203(n) - A178142(n). - Amiram Eldar, Aug 03 2024
MATHEMATICA
a[n_] := DivisorSigma[1, n] - {0, 2, 3, 2, 0, 5}[[Mod[n-1, 6] + 1]]; Array[a, 100] (* Amiram Eldar, Aug 03 2024 *)
PROG
(PARI) a(n) = sigma(n) - [0, 2, 3, 2, 0, 5][(n-1) % 6 + 1]; \\ Amiram Eldar, Aug 03 2024
CROSSREFS
Sequence in context: A309102 A080703 A284682 * A047575 A014097 A219331
KEYWORD
nonn
AUTHOR
Juri-Stepan Gerasimov, Dec 07 2009, Apr 20 2010.
EXTENSIONS
Definition and some values corrected by R. J. Mathar, Jun 07 2010
STATUS
approved