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Search: id:A053707
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| A053707 |
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First differences of A025475, powers of a prime but not prime. |
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+0
11
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| 3, 4, 1, 7, 9, 2, 5, 17, 15, 17, 40, 4, 3, 41, 74, 13, 33, 54, 18, 151, 17, 96, 104, 112, 120, 63, 307, 38, 312, 168, 199, 139, 10, 12, 192, 408, 316, 356, 240, 375, 393, 424, 128, 288, 912, 320, 298, 30, 1032, 271, 1217, 792, 408, 840, 432, 286, 602, 1872, 984, 504
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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In the graph of this sequence, the lowest curve corresponds to differences of squares of twin primes; the next-lowest curve is for squares of adjacent primes differing by 4, etc. - T. D. Noe, Aug 03 2007
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LINKS
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T. D. Noe, Table of n, a(n) for n=1..10000
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FORMULA
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a(n) = A025475(n+1) - A025475(n).
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EXAMPLE
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2^0 = 1 is the first number that meets the definition of A025475, the next one is 2^2 = 4, hence a(1) = 4 - 1 = 3.
a(3) = A025475(4) - A025475(3) = 9 - 8 = 1; a(11) = A025475(12) - A025475(11) = 121 - 81 = 40.
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PROGRAM
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(PARI) {k=1; for(n=2, 16300, if(matsize(factor(n))[1]==1&&factor(n)[1, 2]>1, d=n-k; print1(d, ", "); k=n))} (from Klaus Brockhaus)
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CROSSREFS
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Cf. A025475.
Sequence in context: A076446 A053289 A076412 this_sequence A075052 A111516 A116392
Adjacent sequences: A053704 A053705 A053706 this_sequence A053708 A053709 A053710
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KEYWORD
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nonn
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AUTHOR
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Labos E. (labos(AT)ana.sote.hu), Feb 14 2000
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EXTENSIONS
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Edited by Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), Sep 25 2003
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