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A181790
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Numbers k such that k concatenated with itself is a pandigital biperiod square.
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3
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183673469387755102041, 326530612244897959184, 734693877551020408164, 132231404958677685950413223140496, 206611570247933884297520661157025, 297520661157024793388429752066116, 404958677685950413223140495867769
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OFFSET
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1,1
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REFERENCES
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R. Ondrejka, Problem 1130: Biperiod Squares, Journal of Recreational Mathematics, Vol. 14:4 (1981-82), 299. Solution by F. H. Kierstead, Jr., JRM, Vol. 15:4 (1982-83), 311-312.
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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 A181790_gen(): # generator of terms
for j in count(9):
b = 10**j
a = b*10+1
for k in sorted(sqrt_mod(0, a, all_roots=True)):
if a*b <= k**2 < a*(a-1) and len(set(str(m:=k**2//a))) == 10:
yield m
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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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