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A295654
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Numbers k such that tau(k) +- 1 is congruent to 0 (mod k), where tau is the Ramanujan tau function (A000594).
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1
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OFFSET
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1,2
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COMMENTS
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LINKS
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FORMULA
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EXAMPLE
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tau(11) = 534612 and 11 | (534612 - 1).
tau(23) = 18643272 and 23 | (18643272 - 1).
tau(691) = -2747313442193908 and 691 | (-2747313442193908 - 1).
tau(5807) = 237456233554906855056 and 5807 | (237456233554906855056 + 1).
tau(85583) = 90954516543892718450139576 and 85583 | (90954516543892718450139576 - 1).
tau(189751) = 4685230754227867924094547904 and 189751 | (4685230754227867924094547904 + 1).
tau(37264081) = 831105005803795341334403814220760726696052 and 37264081 | (831105005803795341334403814220760726696052 - 1).
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MATHEMATICA
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fQ[n_] := Block[{t = RamanujanTau@n}, Mod[t, n] == 1 || Mod[t, n] + 1 == n]; (* Robert G. Wilson v, Nov 25 2017 *)
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PROG
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(Python)
from itertools import count, islice
from sympy import divisor_sigma
def A295654_gen(startvalue=1): # generator of terms >= startvalue
return filter(lambda n: n==1 or abs(-840*(pow(m:=n+1>>1, 2, n)*(0 if n&1 else pow(m*divisor_sigma(m), 2, n))+(sum(pow(i, 4, n)*divisor_sigma(i)*divisor_sigma(n-i) for i in range(1, m))<<1)) % n)==1, count(max(startvalue, 1)))
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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