cp's OEIS Frontend

A116210 Numbers k such that k concatenated with k+7 gives the product of two numbers which differ by 8.

%I A116210 #9 Feb 22 2024 15:13:29
%S A116210 73,101,466,577,913,938,1027699544347561123497066503878337002,
%T A116210 1043891904746431592729642732987859418,
%U A116210 1406975496023772119400647610836667853,3905041089422306453928649115284570106,4582028691256280367677282506239892877,4616148891509946292221374856300250093
%N A116210 Numbers k such that k concatenated with k+7 gives the product of two numbers which differ by 8.
%e A116210 938//945 = 965 * 973, where // denotes concatenation.
%o A116210 (Python)
%o A116210 from itertools import count, islice
%o A116210 from sympy import sqrt_mod
%o A116210 def A116210_gen(): # generator of terms
%o A116210     for j in count(0):
%o A116210         b = 10**j
%o A116210         a = b*10+1
%o A116210         for k in sorted(sqrt_mod(23,a,all_roots=True)):
%o A116210             if a*(b-7) <= k**2-23 < a*(a-8) and k>4:
%o A116210                 yield (k**2-23)//a
%o A116210 A116210_list = list(islice(A116210_gen(),10)) # _Chai Wah Wu_, Feb 22 2024
%Y A116210 Cf. A116202, A116209, A116211, A116223, A116341.
%K A116210 nonn,base
%O A116210 1,1
%A A116210 _Giovanni Resta_, Feb 06 2006
%E A116210 a(10)-a(12) from _Chai Wah Wu_, Feb 22 2024