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A005731
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Related to n-th powers of polynomials.
(Formerly M0427)
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4
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1, 1, 2, 3, 2, 5, 2, 21, 2, 3, 1, 55, 3, 13, 2, 21, 2, 85, 1, 57, 2, 1, 1, 8855, 2, 15, 2, 39, 1, 29, 10, 651, 2, 1, 2, 935, 1, 37, 2, 399, 1, 2665, 1, 129, 2, 1, 1, 416185, 2, 21, 2, 15, 1, 4505, 2, 39, 14, 1, 1, 357599, 1, 305, 2, 651, 6, 5, 1, 201, 2, 39, 1, 10687985, 2, 73, 2
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,3
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REFERENCES
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N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
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FORMULA
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PROG
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(Python)
from itertools import count
from sympy import nextprime
c, p = 1, 2
while p < n:
if n%p:
for m in count(2):
if (p**m-1)//(p-1) > n:
break
for r in count(1):
q = (p**(m*r)-1)//(p**r-1)
if q > n:
break
if not n % q:
c *= p
break
else:
continue
if q <= n:
break
p = nextprime(p)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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