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A360790
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Squared length of diagonal of right trapezoid with three consecutive prime length sides.
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1
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8, 13, 41, 53, 137, 173, 305, 397, 533, 877, 977, 1373, 1697, 1885, 2245, 2813, 3517, 3737, 4493, 5077, 5345, 6277, 6953, 7937, 9413, 10217, 10613, 11465, 12077, 12785, 16165, 17165, 18869, 19325, 22237, 22837, 24665, 26605, 27925, 29933, 32141, 32765, 36497, 37253, 38953, 39745
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OFFSET
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1,1
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COMMENTS
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The value d is the square of the length of the diagonal of a trapezoid with a height and bases that are consecutive primes, respectively. The diagonal length is calculated using the Pythagorean theorem, but this distance is squared so that the value is an integer.
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LINKS
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FORMULA
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a(n) = prime(n)^2 + (prime(n+2)-prime(n+1))^2.
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EXAMPLE
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p(2)=3
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a(1): | \ d^2=2^2+(5-3)^2=8
p(1)=2 |_ _ _ _ _\
p(3)=5
p(3)=5
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a(2): | \ d^2=3^2 + (7-5)^2 = 9+4 = 13
p(2)=3 | \
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p(4)=7
a(3)= 5^2+(11-7)^2 = 25+16 = 41
a(7)= 17^2+(23-19)^2=305 = 5*61
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MATHEMATICA
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Map[(#[[1]]^2 + (#[[3]] - #[[2]])^2) &, Partition[Prime[Range[50]], 3, 1]] (* Amiram Eldar, Feb 24 2023 *)
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PROG
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(MATLAB) %shorter 1 line version
arrayfun(@(p) p^2+(nextprime(nextprime(p+1)+1)-nextprime(p+1))^2, [primes(10^6)])
(PARI) a(n) = prime(n)^2 + (prime(n+2)-prime(n+1))^2; \\ Michel Marcus, Feb 23 2023
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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