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Search: id:A135286
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| A135286 |
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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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| 20, 46, 160, 352, 940, 1822, 3670, 5284, 10510, 11800, 19192, 22678, 32590, 37060, 39430, 52222, 57868, 73180, 79834, 97690, 121522, 176830, 187084, 213964, 273052, 325498, 360616, 382564, 412822, 436408, 656920, 676510, 686440, 737044, 778942, 1041430, 1066072, 1103560, 1128934, 1193614, 1328332, 1514176, 1634572, 1665400, 1696522, 1743826, 2040634, 2109784, 2197810, 2215750
(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 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: A044097 A044478 A145220 this_sequence A053245 A115882 A007589
Adjacent sequences: A135283 A135284 A135285 this_sequence A135287 A135288 A135289
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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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EXTENSIONS
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All the entries were wrong. They have been corrected by Franklin T. Adams-Watters, Apr 29 2008
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