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A116254
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k times k+4 gives the concatenation of two numbers m and m-5.
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5
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89, 9077, 9899, 733672, 998999, 88225293, 99989999, 8900869206, 9296908810, 9604060395, 9999899999, 326666333265, 673333666732, 700730927006, 972603739725, 999998999999, 34519562953735, 39737862788836, 49917309624954, 50082690375043, 60262137211161, 65480437046262
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OFFSET
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1,1
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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 A116254_gen(): # generator of terms
for j in count(0):
b = 10**j
a = b*10+1
for k in sorted(sqrt_mod(-1, a, all_roots=True)):
m = (k**2+1)//a
if a*(b+4) <= k**2+1 < a*(a+3):
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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EXTENSIONS
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STATUS
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approved
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