A116268 Numbers k such that k*(k+5) gives the concatenation of two numbers m and m-3.

81, 77394227, 89158933, 36623663376237623663376335, 37633762366336633762366235, 62366237633663366237633761, 63376336623762376336623661, 86194223018927804587702128, 88063202723646452838040443, 35574229497606875609044578088011, 35693849662968953146129859753682, 42317841210726174031503123524229

Offset: 1

Author

Giovanni Resta, Feb 06 2006

Keywords

• nonn
• base

Examples

			89158933 * 89158938 = 79493157//79493154, where // denotes concatenation.
		

Links

• Robert Israel, Table of n, a(n) for n = 1..220

Crossrefs

Cf. A028557, A116099, A116261, A116267, A116269, A116276.

Programs

Maple

f:= proc(d) local k, K;
      K:= map(t -> rhs(op(t)), [msolve(k^2+5*k+3=0,10^d+1)]);
      op(sort(select(k -> k^2 + 5*k + 3 >= (10^d+1)*10^(d-1), K)));
end proc:
map(f, [$1..62]); # Robert Israel, Jul 10 2025

Extensions

More terms from Robert Israel, Jul 10 2025