A116267 - OEIS

%I #16 Feb 19 2024 19:45:35

%S 8,98,426,571,725,844,998,7808,9998,36363,63634,99998,326732,673265,

%T 999998,4545452,5454545,9999998,47058821,52941176,99999998,331983805,

%U 332667332,384615384,422892896,475524475,524475522,577107101,615384613,667332665,668016192,719964244

%N Numbers k such that k*(k+4) gives the concatenation of two numbers m and m-3.

%H Chai Wah Wu, <a href="/A116267/b116267.txt">Table of n, a(n) for n = 1..10000</a>

%o (Python)

%o from itertools import count, islice

%o from sympy import sqrt_mod

%o def A116267_gen(): # generator of terms

%o     for j in count(0):

%o         b = 10**j

%o         a = b*10+1

%o         for k in sorted(sqrt_mod(1,a,all_roots=True)):

%o             if a*(b+3) <= k**2-1 < a*(a+2):

%o                 yield k-2

%o A116267_list = list(islice(A116267_gen(),20)) # _Chai Wah Wu_, Feb 19 2024

%Y Cf. A116136, A116260, A116266, A116268, A116275.

%K nonn,base

%O 1,1

%A _Giovanni Resta_, Feb 06 2006

%E a(29)-a(32) from _Chai Wah Wu_, Feb 19 2024