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Search: id:A135284
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| A135284 |
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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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| 3, 1, 7, 7, 19, 25, 49, 43, 97, 79, 127, 121, 169, 187, 169, 217, 211, 259, 253, 277, 277, 409, 403, 403, 475, 541, 583, 595, 625, 511, 799, 817, 799, 835, 745, 1009, 1015, 1039, 1033, 1033, 1075, 1183, 1267, 1279, 1285, 1213, 1405, 1423, 1477, 1369, 1597, 1573
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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The case for bottom - top + next top produces A006512(n+1), the upper twin primes > 5.
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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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Adjacent sequences: A135281 A135282 A135283 this_sequence A135285 A135286 A135287
Sequence in context: A132307 A101748 A058606 this_sequence A016647 A091039 A120472
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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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