A074372 1 + the sum of the distinct primes dividing n.

1, 3, 4, 3, 6, 6, 8, 3, 4, 8, 12, 6, 14, 10, 9, 3, 18, 6, 20, 8, 11, 14, 24, 6, 6, 16, 4, 10, 30, 11, 32, 3, 15, 20, 13, 6, 38, 22, 17, 8, 42, 13, 44, 14, 9, 26, 48, 6, 8, 8, 21, 16, 54, 6, 17, 10, 23, 32, 60, 11, 62, 34, 11, 3, 19, 17, 68, 20, 27, 15, 72, 6, 74, 40, 9, 22, 19, 19, 80, 8

Offset: 1

Author

W. Neville Holmes, Aug 22 2002

Keywords

• easy
• nonn

Comments

Number of maximal subgroups in dihedral group of order 2n. - Eric M. Schmidt, Oct 14 2014

Examples

			2: 3 (1+2); 3: 4 (1+3); 4: 3 (1+2); 5: 6 (1+5); 6: 6 (1+2+3); ...
		

Links

• Neville Holmes, Integer Sequences

Crossrefs

Cf. A001414, A008472, A036288.

Programs

Maple

with(numtheory): a:=proc(n) local F: F:=convert(factorset(n),list): 1+sum(F[j],j=1..nops(F)) end: seq(a(n),n=1..90); # Emeric Deutsch, Mar 12 2005

Mathematica

Rest[ Range[0, 20] CoefficientList[ Log[E, Series[(1/(1 - x)) Product[ 1/(1 - x^Prime[j]), {j, 200}], {x, 0, 20}]], x]] (* Robert G. Wilson v, Aug 16 2011 *)
Join[{1},Array[1+Total[FactorInteger[#][[All,1]]]&,80,2]] (* Harvey P. Dale, Sep 18 2022 *)

Formula

a(n) = 1 + A008472(n).

Extensions

Corrected and extended by Emeric Deutsch, Mar 12 2005