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Search: id:A076886
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| A076886 |
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Smallest palindrome with exactly n prime factors (counted with multiplicity). |
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+0
1
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| 1, 2, 4, 8, 88, 252, 2772, 27872, 2112, 4224, 8448, 44544, 48384, 2977792, 27011072, 405504, 4091904, 441606144, 405909504, 886898688, 677707776, 4285005824, 276486684672, 21128282112, 633498894336, 2701312131072, 8691508051968
(list; graph; listen)
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OFFSET
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0,2
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EXAMPLE
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a(4)=88 because 88 is the smallest palindromic number with 4 prime factors, 2^3*11 (counted with multiplicity).
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MATHEMATICA
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f[n_] := Length[ Flatten[ Table[ # [[1]], { # [[2]]}] & /@ FactorInteger[n]]]; a = Table[0, {50}]; Do[b = IntegerDigits[n]; c = FromDigits[ Join[b, Drop[ Reverse[b], 1]]]; d = FromDigits[ Join[ b, Reverse[b]]]; e = f[c]; If[ a[[e + 1]] == 0 || a[[e + 1]] > c, a[[e + 1]] = c]; e = f[d]; If[ a[[e + 1]] == 0 || a[[e + 1]] > d, a[[e + 1]] = d], {n, 1, 18697304}]
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CROSSREFS
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Sequence in context: A018580 A089337 A088114 this_sequence A046385 A068664 A018605
Adjacent sequences: A076883 A076884 A076885 this_sequence A076887 A076888 A076889
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KEYWORD
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base,nonn
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AUTHOR
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Shyam Sunder Gupta (guptass(AT)rediffmail.com), Nov 25 2002
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EXTENSIONS
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Edited and extended by Robert G. Wilson v (rgwv(AT)rgwv.com), Dec 02 2002
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