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A116288
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Numbers k such that k*(k+4) gives the concatenation of a number m with itself.
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6
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7, 97, 451, 546, 689, 854, 997, 4380, 5617, 9997, 72728, 99997, 346531, 653466, 999997, 9090906, 9999997, 94117644, 99999997, 334665331, 336032385, 378253326, 390977440, 439928489, 483516484, 516483513, 560071508
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OFFSET
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1,1
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COMMENTS
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Contains 10^m - 3 hence the sequence is infinite. - David A. Corneth, Feb 20 2024
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LINKS
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PROG
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(Python)
from itertools import count, islice
from sympy import sqrt_mod
def A116288_gen(): # generator of terms
for j in count(0):
b = 10**j
a = b*10+1
for k in sorted(sqrt_mod(4, a, all_roots=True)):
if a*b <= k**2-4 < a*(a-1):
yield k-2
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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STATUS
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approved
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