A116170 Numbers k such that k concatenated with k+2 gives the product of two numbers which differ by 1.

590, 738, 830, 1080, 4508, 20660, 29754, 980300, 6694218, 49826988, 117738578, 131505858, 132231404, 176445054, 177285320, 247979808, 252028388, 335180054, 336337790, 404958680, 406231130, 431477468, 499519478

Offset: 1

Author

Giovanni Resta, Feb 06 2006

Keywords

• nonn
• base

Links

• Robert Israel, Table of n, a(n) for n = 1..9000

Crossrefs

Cf. A116163, A116171, A116099, A116301.

Programs

Maple

As:= {}:
for m from 2 to 20 do
   acands:= map(t -> rhs(op(t)), [msolve(a*(a+1)=2, 10^m+1)]);
   bcands:= map(t -> t*(t+1) mod 10^m, acands);
   good:= select(t -> bcands[t]>=10^(m-1), [$1..nops(acands)]);
   As:= As union convert(bcands[good], set);
od: map(t -> t-2, sort(convert(As, list))); # Robert Israel, Aug 20 2019