A107473 Sum of numerator and denominator of Product_{p|n, p prime} (1 - 1/p).
2, 3, 5, 3, 9, 4, 13, 3, 5, 7, 21, 4, 25, 10, 23, 3, 33, 4, 37, 7, 11, 16, 45, 4, 9, 19, 5, 10, 57, 19, 61, 3, 53, 25, 59, 4, 73, 28, 21, 7, 81, 9, 85, 16, 23, 34, 93, 4, 13, 7, 83, 19, 105, 4, 19, 10, 31, 43, 117, 19, 121, 46, 11, 3, 113, 43, 133, 25, 113, 47, 141, 4, 145, 55, 23, 28
Offset: 1
Keywords
Examples
a(12) = 4 = 1+3 because (1 - 1/2)(1 - 1/3) = 1/3.
Programs
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Maple
a:=proc(n) local b,ct,f; with(numtheory): b:=convert(factorset(n),list): ct:=nops(b): f:=simplify(product(1-1/b[j],j=1..ct)):numer(f)+denom(f) end: seq(a(n),n=1..100); # Emeric Deutsch, May 28 2005
Formula
Extensions
More terms from Emeric Deutsch, May 28 2005