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Search: id:A120635
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| A120635 |
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Replace each prime power in the prime-factorizaton of n with the next higher prime-power. |
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+0
3
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| 1, 3, 4, 5, 7, 12, 8, 9, 11, 21, 13, 20, 16, 24, 28, 17, 19, 33, 23, 35, 32, 39, 25, 36, 27, 48, 29, 40, 31, 84, 32, 37, 52, 57, 56, 55, 41, 69, 64, 63, 43, 96, 47, 65, 77, 75, 49, 68, 53, 81, 76, 80, 59, 87, 91, 72, 92, 93, 61, 140, 64, 96, 88, 67, 112, 156, 71, 95, 100, 168, 73
(list; graph; listen)
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OFFSET
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1,2
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EXAMPLE
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12 = 2^2 *3^1. 5 is the prime power closest to 2^2 and larger than 2^2. 4 is the prime power closest to 3 and larger than 3. So a(12) = 5*4 = 20.
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PROGRAM
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(PARI) { a(n) = local(f, r, k, d); f=factorint(n); r=1; for(i=1, matsize(f)[1], k=f[i, 1]^f[i, 2]+1; while(!isprime(k) && (!ispower(k, NULL, &d)||!isprime(d)), k++); r*=k); r } - Max Alekseyev (maxal(AT)cs.ucsd.edu), Feb 01 2007 [Remove "NULL" before running]
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CROSSREFS
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Cf. A120636.
Adjacent sequences: A120632 A120633 A120634 this_sequence A120636 A120637 A120638
Sequence in context: A095880 A076497 A046413 this_sequence A113533 A023713 A032890
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KEYWORD
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nonn
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AUTHOR
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Leroy Quet (qq-quet(AT)mindspring.com), Jun 22 2006
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EXTENSIONS
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More terms from Max Alekseyev (maxal(AT)cs.ucsd.edu), Feb 01 2007
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