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A014684
In the sequence of positive integers subtract 1 from each prime number.
12
1, 1, 2, 4, 4, 6, 6, 8, 9, 10, 10, 12, 12, 14, 15, 16, 16, 18, 18, 20, 21, 22, 22, 24, 25, 26, 27, 28, 28, 30, 30, 32, 33, 34, 35, 36, 36, 38, 39, 40, 40, 42, 42, 44, 45, 46, 46, 48, 49, 50, 51, 52, 52, 54, 55, 56, 57, 58, 58, 60, 60, 62, 63, 64, 65, 66, 66, 68, 69, 70, 70, 72
OFFSET
1,3
LINKS
FORMULA
a(n) = A005171(n) + n - 1.
a(n) = phi(n!)/phi((n-1)!). - Vladeta Jovovic, Nov 30 2002
For n > 3: a(n) = A113523(n) = A179278(n). - Reinhard Zumkeller, Jul 08 2010
a(n) = n - A010051(n). - Reinhard Zumkeller, Sep 10 2013
MATHEMATICA
Table[If[PrimeQ[n], n-1, n], {n, 100}] (* Harvey P. Dale, Aug 27 2015 *)
PROG
(Haskell)
a014684 n = n - fromIntegral (a010051 n)
-- Reinhard Zumkeller, Sep 10 2013
(Magma) [n - (IsPrime(n) select 1 else 0): n in [1..80]]; // Bruno Berselli, Jul 18 2016
(Python)
from sympy import isprime
def A014684(n): return n-int(isprime(n)) # Chai Wah Wu, Oct 14 2023
CROSSREFS
KEYWORD
nonn,easy
EXTENSIONS
More terms from Andrew J. Gacek (andrew(AT)dgi.net)
STATUS
approved