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A237039 Semiprimes of the form (2*p)^3 + 1, where p is prime. 6
65, 217, 10649, 195113, 1191017, 45882713, 55742969, 946966169, 2106997769, 2289529433, 2548895897, 10735357817, 26946035993, 54958685609, 77199941513, 131561576057, 132495001193, 440016501017, 456888832409, 623273556089, 848202406697, 966188398457 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
Eric Weisstein's World of Mathematics, Semiprime.
Wikipedia, Semiprime.
FORMULA
a(n) = (2*A237038(n))^3 + 1.
EXAMPLE
(2*2)^3 + 1 = 65 = 5*13 is a semiprime, so a(1) = 2.
MATHEMATICA
L = Select[Range[5000], PrimeQ[#] && PrimeQ[(2 #)^2 - 2 # + 1] && PrimeQ[2 # + 1] &]; (2 L)^3 + 1
Select[Table[(2p)^3+1, {p, Prime[Range[1000]]}], PrimeOmega[#]==2&] (* Harvey P. Dale, Jul 21 2021 *)
CROSSREFS
Sequence in context: A175795 A056777 A048512 * A305157 A038637 A158686
KEYWORD
nonn
AUTHOR
Jonathan Sondow, Feb 02 2014
STATUS
approved

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Last modified February 22 02:45 EST 2024. Contains 370239 sequences. (Running on oeis4.)