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Search: id:A113492
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| A113492 |
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Least integers, starting with 1, so ascending descending base exponent transforms all 3-almost primes. |
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+0
2
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| 1, 11, 1, 5, 7, 1, 2, 10, 1, 3, 2, 22, 9, 1, 1
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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This is the 3-almost prime analogy to A113320.
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FORMULA
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a(1) = 1. For n>1: a(n) = min {n>0: SUM[from i = 1 to n] (a(i))^(a(n-i+1)) is a 3-almost prime}. a(n) = min {n>0: SUM[from i = 1 to n] (a(i))^(a(n-i+1)) in A014612}.
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EXAMPLE
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a(1) = 1 by definition.
a(2) = 11 because 1^11 + 11^1 = 12 = 2^2 * 3 is a 3-almost prime (A014612).
a(3) = 1 because 1^1 + 11^11 + 1^1 = 285311670613 = 97 * 40699 * 72271.
a(12) = 22 because 1^22 + 11^2 + 1^3 + 5^1 + 7^10 + 1^2 + 2^1 + 10^7 + 1^5 + 3^1 + 2^11 + 22^1 = 292477454 = 2 * 167 * 875681.
a(13) = 9 because 1^9 + 11^22 + 1^2 + 5^3 + 7^1 + 1^10 + 2^2 + 10^1 + 1^7 + 3^5 + 2^1 + 22^11 + 9^1 = 81402 749971 158062 525053 = 1559 * 792769 * 65863726957643.
a(14) = 1 because 1^1 + 11^9 + 1^22 + 5^2 + 7^3 + 1^1 + 2^10 + 10^2 + 1^1 + 3^7 + 2^5 + 22^1 + 9^11 + 1^1 = 33739011038 = 2 * 4649 * 3628631.
a(15) = 1 because 1^1 + 11^1 + 1^9 + 5^22 + 7^2 + 1^3 + 2^1 + 10^10 + 1^2 + 3^1 + 2^7 + 22^5 + 9^1 + 1^11 + 1^1 = 2384195796169465 = 5 * 22349 * 21336040057.
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CROSSREFS
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Cf. A014612, A113320, A005408, A113122, A113153, A113154, A113336, A113271, A113258, A113257, A113231, A087316, A113208.
Sequence in context: A127991 A110305 A010199 this_sequence A010200 A086320 A095193
Adjacent sequences: A113489 A113490 A113491 this_sequence A113493 A113494 A113495
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KEYWORD
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easy,nonn
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AUTHOR
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Jonathan Vos Post (jvospost3(AT)gmail.com), Jan 10 2006
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