

A167688


Number of ways of factoring n with all factors greater than 1 (a(1)=1 by convention) minus number of nonprime divisors of n.


1



0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 2, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 4, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 2, 0, 0, 0, 5, 0, 0, 0, 0, 0, 0, 0, 6, 0, 0, 0, 0, 0, 0, 0, 4, 1, 0, 0, 2, 0, 0, 0, 1, 0, 2, 0, 0, 0, 0, 0, 9, 0, 0, 0, 2, 0, 0, 0, 1, 0
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OFFSET

1,32


LINKS



FORMULA



MATHEMATICA

c[1, r_] := c[1, r] = 1; c[n_, r_] := c[n, r] = Module[{d, i}, d = Select[Divisors@ n, 1 < # <= r &]; Sum[c[n/d[[i]], d[[i]]], {i, 1, Length@ d}]]; Array[c[#, #]  DivisorSum[#, 1 &, ! PrimeQ@ # &] &, 105] (* Michael De Vlieger, Jul 12 2017, after Dean Hickerson at A001055 *)


PROG

(PARI)
fcnt(n, m) = {local(s); s=0; if(n == 1, s=1, fordiv(n, d, if((d > 1) && (d <= m), s=s+fcnt(n/d, d)))); s};


CROSSREFS



KEYWORD

nonn


AUTHOR



EXTENSIONS



STATUS

approved



