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A121315
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Products of two consecutive prime powers.
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1
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2, 6, 12, 20, 35, 56, 72, 99, 143, 208, 272, 323, 437, 575, 675, 783, 899, 992, 1184, 1517, 1763, 2021, 2303, 2597, 3127, 3599, 3904, 4288, 4757, 5183, 5767, 6399, 6723, 7387, 8633, 9797, 10403, 11021, 11663, 12317, 13673, 15125, 15875, 16256, 16768
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OFFSET
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1,1
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COMMENTS
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For some algorithms for finding A034699(n), the numbers in this sequence represent a worst-case scenario of execution time.
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LINKS
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FORMULA
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EXAMPLE
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437 = 19*23 and none of the intervening integers (20,21,22) are prime powers.
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MATHEMATICA
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t = Join[{1}, Select[Range[2, 131], Mod[ #, # - EulerPhi[ # ]] == 0 &]]; Most@t*Rest@t (* Robert G. Wilson v, Sep 02 2006 *)
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PROG
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(PARI) lista(nn) = v = concat(1, select(x->isprimepower(x), vector(nn, n, n))); for (n=1, #v-1, print1(v[n]*v[n+1], ", ")); \\ Michel Marcus, Mar 20 2015
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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