A156858 Composite numbers k such that sum of prime factors of k + number of prime factors of k = prime.

6, 14, 18, 24, 26, 30, 38, 56, 66, 70, 72, 74, 86, 90, 96, 98, 104, 120, 126, 130, 134, 138, 150, 152, 154, 158, 162, 174, 190, 194, 198, 206, 218, 224, 238, 248, 254, 266, 280, 286, 288, 294, 296, 306, 310, 318, 326, 338, 342, 344, 350, 354, 360, 370, 378, 386

Offset

1,1

Links

Table of n, a(n) for n=1..56.

Example

6(2+3+2=7), 14(2+7+2=11), 18(2+3+3+3=11), 24(2+2+2+3+4=13), 26(2+13+2=17), 30(2+3+5+3=13), 38(2+19+2=23), 56(2+2+2+7+4=17)

Mathematica

fQ[n_] := Block[ {fi = Flatten[ Table[ First@#, {Last@#}] & /@ FactorInteger@n]}, !PrimeQ@n && PrimeQ[ Plus @@ fi + Length@ fi]]; Rest@ Select[ Range@ 400, fQ@# &] (* Robert G. Wilson v, Mar 14 2009 *)

Crossrefs

Cf. A000040, A002808.

Sequence in context: A108977 A260114 A340634 * A032500 A053474 A072204

Adjacent sequences: A156855 A156856 A156857 * A156859 A156860 A156861

Keyword

nonn

Author

Juri-Stepan Gerasimov, Mar 12 2009, May 10 2009

Extensions

a(39)-a(56) from Robert G. Wilson v, Mar 14 2009

Status

approved