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 A136155 Composites one larger than a prime and with exactly two or three distinct prime factors. 5
 6, 12, 14, 18, 20, 24, 30, 38, 42, 44, 48, 54, 60, 62, 68, 72, 74, 80, 84, 90, 98, 102, 104, 108, 110, 114, 132, 138, 140, 150, 152, 158, 164, 168, 174, 180, 182, 192, 194, 198, 200, 212, 224, 228, 230, 234, 240, 242, 252, 258, 264, 270, 272, 278, 282, 284, 294 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Robert Israel, Table of n, a(n) for n = 1..10000 FORMULA Union of A136151 and A136152. Subset of A008864. - R. J. Mathar, Apr 24 2008 A136151 UNION A136152. - R. J. Mathar, May 03 2008 EXAMPLE a(1)=6, which is one larger than the prime 5 and has 2 distinct prime factors (namely 2 and 3). 60 is in the sequence because 59 is prime and 60 = 2^2*3*5 has three distinct prime factors. MAPLE A001221 := proc(n) nops(numtheory[factorset](n)) ; end: isA136155 := proc(n) if isprime(n-1) then RETURN( A001221(n)=2 or A001221(n)= 3) ; else RETURN(false) ; fi ; end: for n from 1 to 300 do if isA136155(n) then printf("%d, ", n) ; fi ; od: # R. J. Mathar, May 03 2008 MATHEMATICA okQ[n_] := PrimeQ[n-1] && (PrimeNu[n]==2 || PrimeNu[n]==3); Select[Range[6, 300, 2], okQ] (* Jean-François Alcover, Feb 04 2023 *) CROSSREFS Cf. A136151, A136152, A136153, A136154. Sequence in context: A348251 A290648 A336549 * A315599 A136151 A315600 Adjacent sequences: A136152 A136153 A136154 * A136156 A136157 A136158 KEYWORD easy,nonn AUTHOR Enoch Haga, Dec 16 2007 EXTENSIONS Edited by R. J. Mathar and Jens Kruse Andersen, Apr 24 2008 STATUS approved

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Last modified December 3 01:55 EST 2023. Contains 367530 sequences. (Running on oeis4.)