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A072056
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Number of divisors of 2*prime(n)+1.
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3
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2, 2, 2, 4, 2, 4, 4, 4, 2, 2, 6, 6, 2, 4, 4, 2, 4, 4, 8, 4, 6, 4, 2, 2, 8, 4, 6, 4, 4, 2, 8, 2, 6, 6, 4, 4, 12, 4, 4, 2, 2, 6, 2, 6, 4, 8, 6, 4, 8, 8, 2, 2, 8, 2, 4, 4, 6, 4, 8, 2, 10, 2, 8, 4, 8, 4, 8, 12, 4, 4, 4, 2, 12, 6, 8, 4, 4, 8, 4, 12, 2, 4, 2, 6, 4, 2, 4, 8, 4, 6, 8, 4, 12
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OFFSET
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1,1
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LINKS
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FORMULA
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EXAMPLE
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Divisors of A072055(8) = 2*A000040(8)+1 = 2*19+1=39: {1,3,13,39} with size 4, therefore a(8) = 4.
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MATHEMATICA
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Table[DivisorSigma[0, 2Prime[n]+1], {n, 100}] (* Harvey P. Dale, Apr 12 2021 *)
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PROG
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(PARI) a(n) = numdiv(2*prime(n)+1); \\ Amiram Eldar, Apr 26 2024
(PARI) lista(pmax) = forprime(p = 2, pmax, print1(numdiv(2*p+1), ", ")); \\ Amiram Eldar, Apr 26 2024
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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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