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A124877
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Numbers n such that A007408(n) is prime.
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3
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3, 15, 19, 26, 31, 129, 139, 211, 242, 246, 251, 474, 552, 558, 694, 801, 1001, 1123, 1313, 1687, 4168, 4484, 5611, 6869
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OFFSET
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1,1
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LINKS
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EXAMPLE
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a(1) = 3 since A007408(3)= 251 is the first prime number of sequence A007408,
a(2) = 15 since A007408(15) = 56154295334575853 is the second prime number of sequence A007408.
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MAPLE
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select(isprime@A007408, [$1..200]);
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PROG
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(PARI) num=1; den=1; for(k=2, 2000, k3=k^3; s=(num*k3+den)/(den*k3); num=numerator(s); den=denominator(s); if(isprime(num), print1(k", "))) - Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 26 2008
(Python) # uses A007408gen() and imports from A007408
from sympy import isprime
def agen(): yield from (k for k, ak in enumerate(A007408gen(), 1) if isprime(ak))
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CROSSREFS
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KEYWORD
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hard,more,nonn
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AUTHOR
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EXTENSIONS
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More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 26 2008
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STATUS
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approved
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