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 A239628 Factored over the Gaussian integers, the least positive number having n prime factors counted multiply, including units -1, i, and -i. 3
 1, 9, 2, 6, 4, 12, 8, 16, 48, 144, 32, 96, 64, 192, 128, 256, 768, 2304, 512, 1536, 1024, 3072, 2048, 4096, 12288, 36864, 8192, 24576, 16384, 49152, 32768, 65536, 196608, 589824, 131072, 393216, 262144, 786432, 524288, 1048576, 3145728, 9437184, 2097152 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Here -1, i, and -i are counted as factors. The factor 1 is counted only in a(1). All these numbers of products of 2^k, 3, and 9. Similar to A164073, which gives the least integer having n prime factors (over the Gaussian integers) shifted by 1. LINKS EXAMPLE a(2) = 9 because 9 = 3 * 3. a(3) = 2 because 2 = -i * (1 + i)^2. a(4) = 6 because 6 = -i * (1 + i)^2 * 3. MATHEMATICA nn = 30; t = Table[0, {nn}]; n = 0; found = 0; While[found < nn, n++; cnt = Total[Transpose[FactorInteger[n, GaussianIntegers -> True]][[2]]]; If[cnt <= nn && t[[cnt]] == 0, t[[cnt]] = n; found++]]; t CROSSREFS Cf. A001221, A001222 (integer factorizations). Cf. A078458, A086275 (Gaussian factorizations). Cf. A164073 (least number having n Gaussian factors, excluding units); Cf. A239627 (number of Gaussian factors of n, including units). Cf. A239629, A239630 (similar, but count distinct prime factors). Sequence in context: A298852 A093066 A155168 * A160262 A107821 A154162 Adjacent sequences:  A239625 A239626 A239627 * A239629 A239630 A239631 KEYWORD nonn AUTHOR T. D. Noe, Mar 31 2014 STATUS approved

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Last modified October 19 04:40 EDT 2019. Contains 328211 sequences. (Running on oeis4.)