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a(n) = n + 2 - (number of divisors of n).
2

%I #20 Sep 08 2022 08:45:02

%S 2,2,3,3,5,4,7,6,8,8,11,8,13,12,13,13,17,14,19,16,19,20,23,18,24,24,

%T 25,24,29,24,31,28,31,32,33,29,37,36,37,34,41,36,43,40,41,44,47,40,48,

%U 46,49,48,53,48,53,50,55,56,59,50,61,60,59,59,63,60,67

%N a(n) = n + 2 - (number of divisors of n).

%D L. Comtet, Advanced Combinatorics, Reidel, 1974, p. 121, see #17.

%H Harry J. Smith, <a href="/A059292/b059292.txt">Table of n, a(n) for n = 1..5000</a>

%F a(n) = n + 2 - A000005(n) = A049820(n) + 2. - _Omar E. Pol_, Jul 16 2009

%t Table[n + 2 - DivisorSigma[0, n], {n,1,100}] (* _G. C. Greubel_, Jan 04 2017 *)

%o (PARI) { for (n = 1, 5000, write("b059292.txt", n, " ", n + 2 - numdiv(n)); ) } \\ _Harry J. Smith_, Jun 25 2009

%o (Magma) [n+2-DivisorSigma(0, n): n in [1..100]]; // _Vincenzo Librandi_, Jan 05 2017

%Y Cf. A000005, A049820, A062968. - _Omar E. Pol_, Jul 16 2009

%K nonn

%O 1,1

%A _N. J. A. Sloane_, Jan 25 2001