A116170
Numbers k such that k concatenated with k+2 gives the product of two numbers which differ by 1.
Original entry on oeis.org
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
-
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
A116177
Numbers k such that k concatenated with k+3 gives the product of two numbers which differ by 2.
Original entry on oeis.org
205, 300, 477, 732, 1920, 3157, 52896, 120085, 427020, 8264460, 88581312, 112000885, 112917765, 143075580, 152863360, 193537077, 233788192, 266755221, 313680096, 370908477, 386568925, 440852992, 442670220
Offset: 1
A116296
Numbers k such that k*(k+3) gives the concatenation of two numbers m and m+1.
Original entry on oeis.org
82, 77394228, 89158934, 36623663376237623663376336, 37633762366336633762366236, 62366237633663366237633762, 63376336623762376336623662, 86194223018927804587702129
Offset: 1
89158934 * 89158937 = 79493157//79493158, where // denotes concatenation.
A116230
n times n+7 gives the concatenation of two numbers m and m-9.
Original entry on oeis.org
80, 77394226, 89158932, 36623663376237623663376334, 37633762366336633762366234, 62366237633663366237633760, 63376336623762376336623660, 86194223018927804587702127
Offset: 1
89158932 * 89158939 = 79493157//79493148, where // denotes
concatenation.
A116307
Numbers k such that k*(k+1) gives the concatenation of two numbers m and m+3.
Original entry on oeis.org
83, 77394229, 89158935, 36623663376237623663376337, 37633762366336633762366237, 62366237633663366237633763, 63376336623762376336623663, 86194223018927804587702130
Offset: 1
89158935 * 89158936 = 79493157//79493160, where // denotes concatenation.