A100006 Integer log of 2n: sum of primes dividing 2n (with repetition).

2, 4, 5, 6, 7, 7, 9, 8, 8, 9, 13, 9, 15, 11, 10, 10, 19, 10, 21, 11, 12, 15, 25, 11, 12, 17, 11, 13, 31, 12, 33, 12, 16, 21, 14, 12, 39, 23, 18, 13, 43, 14, 45, 17, 13, 27, 49, 13, 16, 14, 22, 19, 55, 13, 18, 15, 24, 33, 61, 14, 63, 35, 15, 14, 20, 18, 69, 23, 28, 16, 73, 14, 75

Offset

1,1

Links

Table of n, a(n) for n=1..73.

Example

a(20)=11 because 40=2^3*5^1 and 3*2+1*5=11.

Maple

with(numtheory): a:=proc(n) local b: b:=op(2, ifactors(n)): add(b[j][1]*b[j][2], j=1..nops(b)): end: seq(a(2*n), n=1..88); # Emeric Deutsch, Mar 10 2005

Mathematica

Table[Plus @@ Times @@@ FactorInteger[2n], {n, 100}] (* Ray Chandler, Nov 12 2005 *)

Crossrefs

Bisection of A001414.

Sequence in context: A278761 A287076 A344587 * A196262 A238461 A195994

Adjacent sequences: A100003 A100004 A100005 * A100007 A100008 A100009

Keyword

nonn,easy

Author

N. J. A. Sloane, Nov 20 2004

Extensions

More terms from Emeric Deutsch, Mar 10 2005

Status

approved