A116283 - OEIS

%I #9 Aug 01 2021 03:05:48

%S 7,30,64,42753,57241,75423,425072,574922,979528,4301393,5698601,

%T 7028666,4925000747,5074999247,7748266574,8511881484,8814851184,

%U 7059602159672,7106167933828,7439286611621,7485852385777

%N k times k+7 gives the concatenation of two numbers m and m-1.

%o (Python)

%o def ok(n):

%o     s = str(n*(n+7)); h = (len(s)+1)//2; return int(s[:h])-1 == int(s[h:])

%o print(list(filter(ok, range(2, 10**6)))) # _Michael S. Branicky_, Jul 30 2021

%Y Cf. A001704, A028563.

%Y Cf. A116152, A116269, A116282, A116284, A116291.

%K nonn,base

%O 1,1

%A _Giovanni Resta_, Feb 06 2006