A370831 Alternating sum of composites.

4, 2, 6, 3, 7, 5, 9, 6, 10, 8, 12, 9, 13, 11, 14, 12, 15, 13, 17, 15, 18, 16, 19, 17, 21, 18, 22, 20, 24, 21, 25, 23, 26, 24, 27, 25, 29, 26, 30, 27, 31, 29, 33, 30, 34, 31, 35, 33, 36, 34, 38, 36, 39, 37, 40, 38, 42, 39, 43, 41, 44, 42, 45, 43, 47, 44, 48, 45, 49, 46

Offset: 1

Author

James C. McMahon, Mar 02 2024

Keywords

• nonn

Comments

Unlike equivalent sequence for primes, A008347, there are repeated terms.

Examples

			a(4) = 9 - 8 + 6 - 4 = 3.
		

Crossrefs

Cf. A002808, A008347.

Programs

Mathematica

Join[{4},a[1]=4;a[n_]:=ResourceFunction["Composite"][n] - a[n-1];Table[a[n],{n,2,70}]] (* or with signs *) R=70;a[1]=4;a[n_]:=a[n-1]-ResourceFunction["Composite"][n] *(-1)^n;Table[a[n],{n,70}]

Formula

a(n) = A002808(n) - a(n-1), for n>1.