A120535 Semiprimes that are not the sum of 3 pentagonal numbers.
4, 9, 21, 26, 33, 38, 55, 65, 77, 111, 142, 159, 166, 183, 205, 217, 226, 265, 346, 371, 395, 417, 453, 551, 573, 597, 655, 681, 843, 905, 951, 985, 1059, 1165, 1441, 1563, 2033, 2073, 2126, 2361, 2487, 2841, 2991, 3831, 4061, 4601, 8691, 10911
Offset: 1
Programs
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Mathematica
v = #*(3*#-1)/2& @ Range[0, 90]; Select[ Complement[ Range[0, 11000], Union[Total /@ Tuples[{v, v, v}]]], PrimeOmega[#] == 2 &] (* Giovanni Resta, Jun 13 2016 *)
Extensions
Missing a(39) = 2126 from Giovanni Resta, Jun 13 2016
Comments