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Search: id:A135285
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| A135285 |
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Sum of staircase twin primes according to the rule: top * bottom - next top. |
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+0
1
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| 10, 24, 126, 294, 858, 1704, 3528, 5082, 10296, 11526, 18894, 22320, 32208, 36666, 38976, 51744, 57330, 72618, 79212, 96996, 120684, 175968, 186162, 212922, 271914, 324300, 359382, 381282, 411504, 434790, 655278, 674856, 684726, 735282, 776904
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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While there is multiplication and subtraction in the generation of this sequence, it is still called a sum because the arithmetic processes -,*,/ are derived from addition.
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FORMULA
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We list the twin primes in staircase fashion as in A135283. Then a(n) = tl(n) * tu(n) + (-tl(n+1)).
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PROGRAM
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(PARI) g(n) = for(x=1, n, y=twinu(x) * twinl(x) - twinl(x+1); print1(y", ")) twinl(n) = / *The nth lower twin prime. */ { local(c, x); c=0; x=1; while(c<n, if(ispseudoprime(prime(x)+2), c++); x++; ); return(prime(x-1)) } twinu(n) = /* The nth upper twin prime. */ { local(c, x); c=0; x=1; while(c<n, if(isprime(prime(x)+2), c++); x++; ); return(prime(x)) }
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CROSSREFS
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Sequence in context: A067728 A058504 A126911 this_sequence A103071 A057462 A048195
Adjacent sequences: A135282 A135283 A135284 this_sequence A135286 A135287 A135288
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KEYWORD
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nonn
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AUTHOR
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Cino Hilliard (hillcino368(AT)hotmail.com), Dec 03 2007
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