A278935 Least number k = concat(x,y) such that k = n*x*y - x - y, -1 if such a number does not exist.

126, 84, 63, 3231, 42, 4154, 2143, 1143, 4105263158, 6440909347642, 21, 11, 2077, 1077, 18063, 1206, 16056, 105882353, 2052631579, 43304763, 3220454673821, 8044, 12042, 30411, 6039, 5037593985, 321603571507896, 5035, 14033492823, 3033, 17403126122889, 20713030303119

Offset

2,1

Comments

MSD of y can be 0.

Links

Table of n, a(n) for n=2..33.

Giovanni Resta, terms a(2)-a(100) which are smaller than 10^50

Example

a(5) = 3231 = concat(3,231) and 5*3*231 - 3 - 231 = 3231;
a(18) = 16056 = concat(16,056) and 18*16*56 - 16 - 56 = 16056.

Maple

with(numtheory): P:=proc(q) local j, k, s, t, n, ok;
for j from 2 to q do ok:=1; for n from 1 to q do if ok=0 then break; else
for k from 1 to ilog10(n) do s:=n mod 10^k; t:=trunc(n/10^k);
if j*s*t-s-t=n then print(n); ok:=0; break; fi; od; fi; od; od; end: P(10^6);

Crossrefs

Cf. A279058.

Sequence in context: A348898 A267403 A267342 * A267395 A176303 A157321

Adjacent sequences: A278932 A278933 A278934 * A278936 A278937 A278938

Keyword

nonn,base,more

Author

Paolo P. Lava, Dec 02 2016

Extensions

a(10), a(11), a(19)-a(22), a(27), a(28), a(30), a(32), a(33) by Giovanni Resta, Dec 05 2016

Status

approved