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 A111751 Numbers n such that P(3*n + 1) has exactly two distinct prime factors, where P(m) is the partition number A000041. 0
 2, 22, 25, 28, 37, 40, 60, 73, 78, 80, 129, 135, 158, 162, 215, 220, 228, 238, 269, 285, 315, 332, 344, 347, 355, 365, 366, 390, 397, 402, 439, 443, 470, 477, 533, 549, 653, 694, 710, 715, 716, 745, 765, 782, 822 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS EXAMPLE If n=2 then P(3*n + 1) = 15 = 3 x 5 (two distinct prime factors), so the first term is 2. MAPLE with(combinat): with(numtheory): a:=proc(n) if nops(factorset(numbpart(3*n+1)))=2 then n else fi end: seq(a(n), n=1..300); # Emeric Deutsch, Jan 27 2006 MATHEMATICA For[n = 1, n < 550, n++, If[Length[FactorInteger[PartitionsP[3*n + 1]]] == 2, Print[n]]] (* Stefan Steinerberger, Jan 27 2006 *) CROSSREFS Cf. A000041. Sequence in context: A228112 A080433 A022373 * A037416 A057871 A152243 Adjacent sequences:  A111748 A111749 A111750 * A111752 A111753 A111754 KEYWORD nonn AUTHOR Parthasarathy Nambi, Nov 19 2005 EXTENSIONS More terms from Stefan Steinerberger and Emeric Deutsch, Jan 27 2006 More terms from Emeric Deutsch, Jan 30 2006 STATUS approved

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Last modified September 25 15:00 EDT 2021. Contains 347657 sequences. (Running on oeis4.)