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A258774
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a(n) = 1 + sigma(n) + sigma(n)^2.
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3
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3, 13, 21, 57, 43, 157, 73, 241, 183, 343, 157, 813, 211, 601, 601, 993, 343, 1561, 421, 1807, 1057, 1333, 601, 3661, 993, 1807, 1641, 3193, 931, 5257, 1057, 4033, 2353, 2971, 2353, 8373, 1483, 3661, 3193, 8191, 1807, 9313, 1981, 7141, 6163, 5257, 2353
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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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MAPLE
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MATHEMATICA
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Table[1 + DivisorSigma[1, n] + DivisorSigma[1, n]^2, {n, 10000}]
Table[Cyclotomic[3, DivisorSigma[1, n]], {n, 10000}]
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PROG
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(Magma) [1+SumOfDivisors(n)+ SumOfDivisors(n)^2: n in [1..50]]; // Vincenzo Librandi, Jun 10 2015
(Python)
from sympy import divisor_sigma
....return (lambda x: x*(x+1)+1)(divisor_sigma(n)) # Chai Wah Wu, Jun 10 2015
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CROSSREFS
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Cf. A000203 (sum of divisors of n).
Cf. A258775 (indices of primes in this sequence), A258776 (corresponding primes).
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KEYWORD
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easy,nonn
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AUTHOR
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STATUS
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approved
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