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A085927
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a(n) is the digitwise absolute difference between the n-th palindrome and its 9's complement.
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1
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7, 5, 3, 1, 1, 3, 5, 7, 9, 77, 55, 33, 11, 11, 33, 55, 77, 99, 797, 777, 757, 737, 717, 717, 737, 757, 777, 797, 595, 575, 555, 535, 515, 515, 535, 555, 575, 595, 393, 373, 353, 333, 313, 313, 333, 353, 373, 393, 191, 171, 151, 131, 111, 111, 131, 151, 171, 191
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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(24) = 717 because A002113(24) = 151 and A061601(151) = 848. 8-1 = 7 and 5-4 = 1, thus 717.
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PROG
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(Python)
from sympy import isprime
from itertools import count, product
def f(s): return int("".join(str(abs(9 - 2*int(c))) for c in s))
def pals(base=10): # all (nonzero) palindromes as strings
digits = "".join(str(i) for i in range(base))
for d in count(1):
for p in product(digits, repeat=d//2):
if d > 1 and p[0] == "0": continue
left = "".join(p); right = left[::-1]
for mid in [[""], digits][d%2]:
t = left + mid + right
if t != '0': yield t
def aupton(nn): p = pals(); return [f(next(p)) for i in range(nn)]
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CROSSREFS
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KEYWORD
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base,easy,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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