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A116254
k times k+4 gives the concatenation of two numbers m and m-5.
5
89, 9077, 9899, 733672, 998999, 88225293, 99989999, 8900869206, 9296908810, 9604060395, 9999899999, 326666333265, 673333666732, 700730927006, 972603739725, 999998999999, 34519562953735, 39737862788836, 49917309624954, 50082690375043, 60262137211161, 65480437046262
OFFSET
1,1
PROG
(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
A116254_list = list(islice(A116254_gen(), 40)) # Chai Wah Wu, Feb 19 2024
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Giovanni Resta, Feb 06 2006
EXTENSIONS
a(19)-a(22) from Chai Wah Wu, Feb 19 2024
STATUS
approved